Misfire Under Load When Warm Up

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09-03-2022, 10:29 PM

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Misfire Under Load When Warm Up

88 Z31 Turbo Shiro, been chasing this weird misfire issue. Starts and idles fine, great throttle response, making the appropriate amount of boost and vacuum I think. However, when you drive it for 10-15 minutes and get it warm, it develops an extremely bad misfire under load and a slight misfire at idle.

FPR is good
Tested the MAF with the procedure on XenonZCar and it tested good
EGR, IACV, CSV have been deleted
New CHTS (relocated)
New vacuum lines

Only does it after it's gotten warmed up and under load. I can rev it all the way to redline no problem in neutral, but trying to go up a hill becomes near undoable under load/boost. No ECU codes either. Only thing I have not tested is hot compression just due to spark plug access with my gauge. I don't think it'd be the CAS getting hot and failing since it's only doing it under load. I don't think it's an injector either since it still starts and idles fine when hot, and runs fine under load until then.

Only theory other than compression I have right now is heat soak to the charge pipe (previous owner installed an aftermarket one) or induction system,causing a misfire under boost when warm.

Any of you guys have any ideas or advice on what to check next?