Hi everyone! So I finished my LHU swap and I have some boosting problems. It still has the LNF hpt tune on it but I'm changing it next weekend so the car won't run until the new tune. Just to make sure what can cause my problems, if it's related to the bad tune or if it's physical mechanic pieces.

The car is fluttering af. Stock bpv. We tried with another one that was functional from another friend cobalt. Same result.

Car boosting at 6 psi max, we tried another map sensor gms1 like I have from another friend cobalt, car started to boost at 22 psi but still has fluttering. We put back mine, car was still boosting at 22 psi with my sensor but 9 hours later (this morning), it came back to 6 psi max.

Vacuum is at 20-21 so looks good.

So what can cause the fluttering and the non constant boost? Can it be tune related or purely mechanical?

Anyone?

yeah like a stututututu noise

Yeah but not in this case, it only does compressor surge and I don't know why. I don't want to drive the car and break something