I just purchased a 2001 A6 4.2. Great care, I really like it. I'm quickly learning that thier are not a whole lot of performance upgrades that you can do to this car at a reasonable price. Does anyone know who offers a good cat back exhaust system for this car. My main objective is to increase performance, not just sound cool.

 

peromance upgrades on the 4.2 are best in the form of superchargers. There is one in development right now - I don't know of any that are already on the market. The cat back exhaust will give you an additional 7-10% increase in HP - not much for the dollar investment.

 

check this:
http://forums.audiworld.com/a6/msgs/187747.phtml