90 gst idle off idle problem

when im on the gas its good let off and it bucks and does the same if your light on the gas. changed plugs, wires. cleaned throttle body. it has an upgraded turbo. even parked giving it gas from under the hood it misses from just off idle to about 2500 rpm. need help im stumped

Have you done a boost leak test? Your problems dont normally occur from a boost leak but its worth a shot. The more you can eliminate the better your chance at getting it fixed.

Welcome to AF

i haven't but my boost stays at 8 psi and holds. i put a new copper head gasket on it when i got it, because the guy i bought it from gave it to me with the car he thought the gasket was blown. i dont remember how it ran when i brought it home because he dont live far from me. I'm pretty sure i have the cams back in time, and im wondering if that would play a part in my problem. it sucks on the first gen to check all the timing marks