Car pulls perfect vaccum, drives fine, even starts doing fine under boost, but the second it hits .4 bars it falls flat on its face. I've checked all the vaccum lines and cant find anything. Up until .4 bars its normal, but the second it hits that, boost drops, the car sounds like its popping out the exhaust (very lightly) and it falls flat on its face. Its converted to non-sequential twins and run by pfc. I have no idea why its doing this. This came out of nowhere.