there is people running over 900whp on the stock bottom end.
you fuel pump with bigger injectors and a BAP will support 650whp
anything around or over 650whp and your stock A6 trans will start to flare the shifts after alittle while. unless you have it built.
no one really no the limits of the stock half shafts or rear end yet. esp if you are not always at the track. a buddy of mines manuel 5th gen puts down over 1100whp and his half shafts and center section are 100% stock for over a year now with no problem.
Procharger F1X, 4L80E, CBI Street Cars, DSX Tuning