ECU code 21 help

[chitrees]

How did you guys go about the diagnosing process for ecu code 21 (ignition circuit signal)?
Also, if your injectors were clogged or not supplying enouh fuel, could this some how have a negative feedback and show up as part of an ignition circuit code?

[Gts_Junior]

To help you out a bit here ignition code 21 is a little broad in the perspective of what ignition part is actually at fault.

1. Are you getting a misfire at high rpm while on throttle? or are you getting a misfire when the car is idling?

2. common remedies and or procedures are to change your spark plugs

3. check for resistance with a multimeter on the coil packs

4. most common is the coil pack wiring harness has probably been damaged from wear and tear, perform a resistance test with a multimeter on the harness it self.

5. check your ignitor pack also which attaches to the coil harness.

[chitrees]

Here's a video: https://www.youtube.com/watch?v=haKpmb5AMl0.

Idling it usually climbs throughout the rpm range.
No boost leaks.
Yes plugs have been changed and gapped numerous times (0.8mm).
And LS2 conversion was done; however, coilpacks were taken off of a '05 Avalanche so I'm not sure if they are actually in 100% working order. Note: there was no change from packs being changed.
Timing is set to 15 degrees.
As far as wiring goes, I've checked with a multi the voltage from the ECU to packs and they are what they should be. However, I haven't checked the wiring from CAS to ECU(the ignition input voltages); I didn't think I would need to.