Feel free to experiment all you wish. Probably worth remembering that euro cars are from a different mindset. As a generality, Yanks measure their cars by standing start accelleration whereas the euro is more about speed on the road. Later Audi are more cross over and have world class standing start accelleration from the ultimate sports models but that is more an outcome of good engines and auto boxes than outright intent.
You may and may not be happy with the outcome and if you aren't, it may be because you're trying to make the car something it isn't. I've had a range of the old supercars and in their day they were rock stars. Now, the basic engineering approach of yesteryear is all too obvious.
C5 RS6: Sportec, Milltek & Wagner -- B5 RS4 : tastefully modified -- Audi 1.8 quattro 132 Kw -- UNIMOG 404 TLF8