I've got an RB20DET with FMIC, AVCR, exhaust, filter and an aftermarket turbo (supposedly a rebuilt RB25) and a reprogrammed ECU.
Hits full boost by about 3500 rpm but then the car feels like its losing power, turbo starts making a shuffling sort of noise, the boost gauge neede starts to dart left and right really quickly. Once above 4500 rpm, the problem goes away and the car pulls hard to 7500rpm.
Is this compressor surge? The turbo is meant to be a stock RB25 unit with steel internals and plain bearings so it shouldnt really happen. If it is surge then its a really bad thing right?