So I have a 2005 Evo 8. Stock engine. Only mods are 3" turboback exhaust,mishimoto intercooler, and full hard pipe kit. Stock bov. Polyurethane front engine mount.

It was tuned at ams about 2 years ago But the problem didn't come till about a year ago. A couple months ago my trans went out so I got a lightned flywheel and exedy clutch and a new trans.

My problem is that it feels like it's misfiring bad under boost but still can get to full boost. I can gradually build boost but I have to slowly press the gas pedal to do it. Like knocking? Sometimes it will boost totally fine. My plugs are NGK BRP8ES and are gapped at .025. They were at around .022 a couple days ago but no change in the problem. Replaced the cam angle sensor today and nothing. Also there is no check engine light.

My list of parts Im thinking about is the knock sensor and the crank sensor. Other than that I'm not sure where to go. Maybe a new tune?

Suggestions are appreciated

 

Gap down to 0.020 or even 0.019" and report back.

 

I have the same issue but using BPR7ES. I will regap my plugs when the weather is a little warmer. I did not have an issue until I installed a Perrin filter after my cam install.