I have talked to a few gm mechanics and they have said the drivetrain is the weakest part of our cars. How much hp can the 04 with an a4 take before i start breaking parts?

There are many pushing over 450 RWHP with no problems yet. But, that seems to be their biggest concern. Haven't heard of too many failures, pretty good for the weakest link.

Edit... I assume you're talking from the transmission back.