my exhaust is 3inches decated. The conrod is using integrated engineering forged. The crank and pistons were balanced.Today tested high boost mode, seems it has some problems so the boost just go straight to 2.0bar, I guess i need to send back for setting again, the car is running very rich in fuel now with 4 RS4 injectors.I am running low boost 1.2bar most of the time. Anyway I am in hk, roads here basically hard to have any fun drive but always met interesting marques like porsche and ferrari so my car still consider a slow car here.
Since i am a newbie and this car is actually a pass on project from my friend( he is going after AMG C63 so he sold the car to me) . I dont know if my answers technical enough to answer your question.