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As many of you know I've had some bad leaning out when under full throttle. I have tested everything to try and find the root cause, and finally today I fixed it lol. So I'm going to walk you threw the steps on how to fix your hesitation/wot throttle problems/ leaning out. Basically you can stop fixing when one of these tests work 
So if one doesn't work, follow next step.
1) Check your ECU for codes. To do so, follow this link [URL=http://forums.gtrcanada.com/showthread.php?t=13657[/url]
While you're doing that test your O2 sensor, it should flash between 5-10 times in 10 seconds. If your codes came back 55 then you'll need to go threw all these step by step If it showed you something, chances are that is your problem Try searching through here to see if you can fix it though.
2.) Check for vacuum leaks- to do this get a propane torch and don't light it, and just run it along all the vacuum lines in your car slowly while the car is running, if the idle jumps, you have a vacuum leak. Replace the vacuum line. Take your car for a ride ( remember to shut off the torch ) and see if this fixes your problem.
3.) Try resetting your ECU --Always start with the cheapest fixes first, and work from there. To do this simply take your negative battery terminal off and step on the brake for about half a minute.
4.) Try adjusting your Throttle position sensor(TPS). To do this manually with a multimeter--yess you'll need one for 2 parts of this howto--Locate your TPS. It is a small black box on your throttle body. Once you've found it you'll see two wires coming out of it-DO NOT TEST THESE WIRES. You want to look under that box, you'll see three wires connecting to your TPS. Your going to want to tap into the middle wire. Now, turn your key to the ON position (inside car) and then go back under your hood. Take the positive probe from your multimeter and tap it to that middle wire, and then ground the negative probe anywhere you can ground it. Now if you see your voltage above .5 you're going to want to reduce it to under. I would go .48 to be safe. If it is above this you will have hesitation problems with the throttle as it starts throwing bad codes. To adjust the sensor just unscrew those two bolts holding the TPS to the throttle body a little bit and wiggle it. This is probably the hardest part using all three of your hands. Anyways adjust it under .5. If it is way lower than .5 then adjust it higher. Do this until you're around .48~.49.
4.)Try cleaning your maf--Hopefully those two things would have solved your problem, but if not continue on to testing your MAF sensor. Your maf sensor is located behind your cone filter (hopefully you have one) or stock airbox. It is a little black cylinder with a box sticking out of it. Once you have removed it be sure that it is cold (haven't driven car for a couple hours) To speed things along put it in the fridge. If you don't do this you will ruin your maf. Now, once it is nice and cool look at your maf, You'll see an ugly sensor behind the mesh screen. Get some Brakeleen or electrical contact cleaner and spray that thing down along with spraying the screen of the sensor (do both sides) and then whipe it down. Let everything cool off and the chemicals to evaporate. Hopefully you will have cleaned the sensor and may fix your problem. Take it for a drive. If not you're going to need to test it more
5.) Resoldering the connections on your maf-First of all before doing this try someone elses Maf sensor that you know is working well. It will save you some time. Follow procedure three to get your maf off the car and once you have done that look at the top of the black box sticking out the side. The top is sealed by rubber. You're going to have to use a exacto knife or something sharp to cut through this rubber part. Once you have done so pop it out (can be difficult use something as a wedge to help it out. Now you will see a copper plate on the top, and then look to where the wires usually plug into the maf on the outside. Now look how they connect to the internal part of the maf. You're going to be resoldering this today So warm your soldering iron up and destroy these connections. Spray them down with electrical contact cleaner (not necessary but advised). Now get some shiny new solder and redo the connections ( don't be afraid to use a lot ) but don't touch the plastic sides as you will melt it haha. Let everything cool off. To reassemble you're going to want to use some INSTANT GASKET. You can find it at canadian tire for about $5.00. Rub that around the sides of the plastic square top you just took off. And reinsert. Let everything dry/set and take it for a drive. If you tested another MAF sensor and it fixed your problems, and this did nothing you need a new maf. If this fixed your problem, GREAT!!! If not, proceed to step 5.
6.) CLEANING/Testing COILS / Change PLUGS/ and goodies
Okay so this is where it gets fun and you'll have to use a strange tool called an Alan key and a spark plug socket. Okay so use the Alan key to take off your spark plug cover. It's that black thing that goes between your valve covers. You'll need to remove some of your intake piping to do this. Once you have it off (see it wasn't hard) You'll see 6 black things, those are your coils, and under them are your sparkplugs Yes I am dumbing this down for the non-technically inclined people. Okay, so first things first if you see any red dust go get your cars timing redone and get new pully's /bearings. If not, proceed! To run a basic test, reconnect your intake piping and start your car. Unplug one coil at a time and see if your car runs like crap. If nothing happens that coil is dead and you need to replace it. If the car runs bad when you unplug them your coils are functioning (okay, maybe good, maybe bad). Now we're going to test for resistance. To do this remove one coil at a time and use the resistance testing function on your multimeter and tap it to the Positive and negative parts of your coils. It should be clear which one is positive and negative as it says right on the coil above where the plug would connect
This should read between .6-.9 ohms. If not in this range you need a new coil. Repeat this on all coils. If changing the coil didn't help, proceed and follow directions on this link:[URL="http://forums.gtrcanada.com/showthread.php?t=16618"[/url]
While you're in there you may as well change your spark plugs.
I recommend BCPR6EIX(iridium) or BCPR6ES(copper). You can also go up to a 7 grade plug as well if you wish, but isn't needed.
7.) Test your Igniter pack -- I hope the above solved your problems, if not your car is sounding like mine and the problem is hidden somewhere. To test your igniter pack you're going to need to get another one (borrow one from another GTRCR) and take it for a ride. If there is a noticeable difference get a new igniter pack. If not, continue 
8.) Checking PCV valve and lines - To do this locate your PCV valve. It will be a weird looking bolt thing connecting to the front most part of your intake manifold. It will have lines going across the engine as well. To remove this, just untwist the bolt.. duh. Be careful with the lines while removing this as they are old and have oil in them (oil eats rubber) and will crack easily. Before removing it pinch all your lines first, if they are hard then buy new lines and replace them as you're doing this step. If they are leaking it will cause issues as well so replace as needed. You can find the rubber hoses at Canadian tire for about 5bucks per 6 feet. Now once you have the PCV valve off and you've changed your broken hoses take some new hose and attach it to the front of the valve and blow. Did any of the air get through (and do you feel light headed from fuems?) If the air came out the other side then good! your PCV valve is fine. If not, replace it.
9.) Changing fuel filter-I sincerely hope your not on this step, but if you are. We're going to talk about fuel systems. This is the nissan part number:16400-53J10 so you can pick that part up at your local parts store. now to locate this look at your engine from the front of your car, look to the left and down. You'll see a metal tin with a line going to it. That is your fuel filter. Now remove these lines. (you might get fuel everywhere!) But if you want to avoid this simply open the fuse box, and pop out the fuel pump fuse and try and start the car. It should drain the lines. Now remove the lines after shutting off your car and replace with new fuel filter (This is probably the hardest part of this howto... Do your hands hurt yet? Now take your car for a drive, see if this solved your problem. Hurray it did? GOOD! If not, try next step .
10.) Test your fuel pressure regulator - To do this locate your fuel pressure regulator. It is located underneith your PCV valve. It's a black looking thing that has a hose going into the intake manifold. Now to test, be careful and remove the hose connecting to the intake manifold. Now you need to plug that hole, to do this simply get something rubber or plasic that will slip over it and plug it. I used a marker cap. Then take something to plug the rubber hose as well ( i used a screw and some tape). Take it for a small drive, but a SMALL one. See if this solves your issue. If not, reconnect. If it did buy a new one.
So if one doesn't work, follow next step.1) Check your ECU for codes. To do so, follow this link [URL=http://forums.gtrcanada.com/showthread.php?t=13657[/url]
While you're doing that test your O2 sensor, it should flash between 5-10 times in 10 seconds. If your codes came back 55 then you'll need to go threw all these step by step
If it showed you something, chances are that is your problem Try searching through here to see if you can fix it though.2.) Check for vacuum leaks- to do this get a propane torch and don't light it, and just run it along all the vacuum lines in your car slowly while the car is running, if the idle jumps, you have a vacuum leak. Replace the vacuum line. Take your car for a ride ( remember to shut off the torch ) and see if this fixes your problem.
3.) Try resetting your ECU --Always start with the cheapest fixes first, and work from there. To do this simply take your negative battery terminal off and step on the brake for about half a minute.
4.) Try adjusting your Throttle position sensor(TPS). To do this manually with a multimeter--yess you'll need one for 2 parts of this howto--Locate your TPS. It is a small black box on your throttle body. Once you've found it you'll see two wires coming out of it-DO NOT TEST THESE WIRES. You want to look under that box, you'll see three wires connecting to your TPS. Your going to want to tap into the middle wire. Now, turn your key to the ON position (inside car) and then go back under your hood. Take the positive probe from your multimeter and tap it to that middle wire, and then ground the negative probe anywhere you can ground it. Now if you see your voltage above .5 you're going to want to reduce it to under. I would go .48 to be safe. If it is above this you will have hesitation problems with the throttle as it starts throwing bad codes. To adjust the sensor just unscrew those two bolts holding the TPS to the throttle body a little bit and wiggle it. This is probably the hardest part using all three of your hands. Anyways adjust it under .5. If it is way lower than .5 then adjust it higher. Do this until you're around .48~.49.
4.)Try cleaning your maf--Hopefully those two things would have solved your problem, but if not continue on to testing your MAF sensor. Your maf sensor is located behind your cone filter (hopefully you have one) or stock airbox. It is a little black cylinder with a box sticking out of it. Once you have removed it be sure that it is cold (haven't driven car for a couple hours) To speed things along put it in the fridge. If you don't do this you will ruin your maf. Now, once it is nice and cool look at your maf, You'll see an ugly sensor behind the mesh screen. Get some Brakeleen or electrical contact cleaner and spray that thing down along with spraying the screen of the sensor (do both sides) and then whipe it down. Let everything cool off and the chemicals to evaporate. Hopefully you will have cleaned the sensor and may fix your problem. Take it for a drive. If not you're going to need to test it more
5.) Resoldering the connections on your maf-First of all before doing this try someone elses Maf sensor that you know is working well. It will save you some time. Follow procedure three to get your maf off the car and once you have done that look at the top of the black box sticking out the side. The top is sealed by rubber. You're going to have to use a exacto knife or something sharp to cut through this rubber part. Once you have done so pop it out (can be difficult use something as a wedge to help it out
. Now you will see a copper plate on the top, and then look to where the wires usually plug into the maf on the outside. Now look how they connect to the internal part of the maf. You're going to be resoldering this today So warm your soldering iron up and destroy these connections. Spray them down with electrical contact cleaner (not necessary but advised). Now get some shiny new solder and redo the connections ( don't be afraid to use a lot ) but don't touch the plastic sides as you will melt it haha. Let everything cool off. To reassemble you're going to want to use some INSTANT GASKET. You can find it at canadian tire for about $5.00. Rub that around the sides of the plastic square top you just took off. And reinsert. Let everything dry/set and take it for a drive. If you tested another MAF sensor and it fixed your problems, and this did nothing you need a new maf. If this fixed your problem, GREAT!!! If not, proceed to step 5.6.) CLEANING/Testing COILS / Change PLUGS/ and goodies
Okay so this is where it gets fun and you'll have to use a strange tool called an Alan key and a spark plug socket. Okay so use the Alan key to take off your spark plug cover. It's that black thing that goes between your valve covers. You'll need to remove some of your intake piping to do this. Once you have it off (see it wasn't hard) You'll see 6 black things, those are your coils, and under them are your sparkplugs
Yes I am dumbing this down for the non-technically inclined people. Okay, so first things first if you see any red dust go get your cars timing redone and get new pully's /bearings. If not, proceed! To run a basic test, reconnect your intake piping and start your car. Unplug one coil at a time and see if your car runs like crap. If nothing happens that coil is dead and you need to replace it. If the car runs bad when you unplug them your coils are functioning (okay, maybe good, maybe bad). Now we're going to test for resistance. To do this remove one coil at a time and use the resistance testing function on your multimeter and tap it to the Positive and negative parts of your coils. It should be clear which one is positive and negative as it says right on the coil above where the plug would connect This should read between .6-.9 ohms. If not in this range you need a new coil. Repeat this on all coils. If changing the coil didn't help, proceed and follow directions on this link:[URL="http://forums.gtrcanada.com/showthread.php?t=16618"[/url]
While you're in there you may as well change your spark plugs.
I recommend BCPR6EIX(iridium) or BCPR6ES(copper). You can also go up to a 7 grade plug as well if you wish, but isn't needed.
7.) Test your Igniter pack -- I hope the above solved your problems, if not your car is sounding like mine and the problem is hidden somewhere
. To test your igniter pack you're going to need to get another one (borrow one from another GTRCR) and take it for a ride. If there is a noticeable difference get a new igniter pack. If not, continue 8.) Checking PCV valve and lines - To do this locate your PCV valve. It will be a weird looking bolt thing connecting to the front most part of your intake manifold. It will have lines going across the engine as well. To remove this, just untwist the bolt.. duh. Be careful with the lines while removing this as they are old and have oil in them (oil eats rubber) and will crack easily. Before removing it pinch all your lines first, if they are hard then buy new lines and replace them as you're doing this step. If they are leaking it will cause issues as well so replace as needed
. You can find the rubber hoses at Canadian tire for about 5bucks per 6 feet. Now once you have the PCV valve off and you've changed your broken hoses take some new hose and attach it to the front of the valve and blow. Did any of the air get through (and do you feel light headed from fuems?) If the air came out the other side then good! your PCV valve is fine. If not, replace it. 9.) Changing fuel filter-I sincerely hope your not on this step, but if you are. We're going to talk about fuel systems
. This is the nissan part number:16400-53J10 so you can pick that part up at your local parts store. now to locate this look at your engine from the front of your car, look to the left and down. You'll see a metal tin with a line going to it. That is your fuel filter. Now remove these lines. (you might get fuel everywhere!) But if you want to avoid this simply open the fuse box, and pop out the fuel pump fuse and try and start the car. It should drain the lines. Now remove the lines after shutting off your car and replace with new fuel filter (This is probably the hardest part of this howto... Do your hands hurt yet? Now take your car for a drive, see if this solved your problem. Hurray it did? GOOD! If not, try next step .10.) Test your fuel pressure regulator - To do this locate your fuel pressure regulator. It is located underneith your PCV valve. It's a black looking thing that has a hose going into the intake manifold. Now to test, be careful and remove the hose connecting to the intake manifold. Now you need to plug that hole, to do this simply get something rubber or plasic that will slip over it and plug it. I used a marker cap. Then take something to plug the rubber hose as well ( i used a screw and some tape). Take it for a small drive, but a SMALL one. See if this solves your issue. If not, reconnect. If it did buy a new one.
. Once you've done that proceed to this link to follow a very good DIY
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