a vishnu tuned 335 with a downpipe, and FMIC keeps up with e60 M5's so i say on the modding front it is already well on its way. I've driven a 335i and it is an amazing car i would definatly choose that over the a4 anyday.

On throwing the vishnu chip in voiding your warranty. It is setup so that it can be removed by the user for a dealer visit and then plugged right back in.

The all wheel drive system that comes on the 335 is a different system than what came with the earlier x5's and e46 xi's. The original system made the car slower off the line and didnt perform that well compared to quattro. The system that comes in the e90/92 is completely revamped and is unreal even though it adds weight to the car with the added traction it makes the car a tad quicker.