RS500

if it's what i'm thinking, it will happen always and it would be pretty audible.

have u leaned it out the turbo by running hi-boost and not having enough fuel? if so, you have probably melted your turbine wheel and caused the turbo to go out of balance which might be causing the exhaust wheel to hit the housing. check the shaft for any movement (in/out & left/right) from the compressor side, or get it checked out by a turbo specialist. good luck.

clint32, fyi, the HKS T04E is actually rated at 500hp and would be perfect for an Rb20DET engine. a little laggier than the standard turbo but power/boost would come on quite hard. check out the following link, it should give u all an indication of the hp ratings fro all the turbo's mentioned. http://www.hksusa.com/categories/?id=1093 btw, a friend has a 400hp GT25 on his R32 RB20DET, along witha FMIC, unichip, and bigger pump and it's producing 222kw at the wheels on 18psi, with heaps more potential. i guess it all depends on what u want from your car joel. //RS500.