I say its the mbc... I would personally try to get a used N75 and see what happens (maybe rent a used vw/audi and swap valves for testing purposes?[&:]). If it doesnt work after that, sell your mbc/n75 to put towards a new wastegate or turbo.

 

If its boosting the SAME with the n75.....ITS NOT THE MBC

 

yeah, there was 0 difference between the MBC and the N75 valve. Both overboost to about 15-16 psi and then I get detonation.

Josh