I recently purchased a 98 A6 with the 2.8L engine. Now that I have been researching I find that the 2.7T and 4.2 are more popular options. I really love this car and am looking for Mods to enhance this awesome experiance. Can you supercharge it and is it worth it? Are there chips available for this yr & engine? I don't believe you can easily put a turbo on it.
I am also wondering the differance between the B4 & C5.

 

Engine: PES Supercharger (chipping produces very little gain)
Suspension: New (lowered) springs & shocks or coilovers (preferred) & H-sport sway bars
Wheels: some nice 17x8 wheels with 235/45 tires
Brakes: Upgrade to improved calipers & SS lines if you plan on supercharging (ya gotta stop once you get going)

Looking to improve fun? Go for the suspension/wheel mods first. Plenty of places you can have fun in the turns - going really fast in a straight line just gets you tickets (wastes good mod money). Keep it balanced (thus the list of NON-engine mods above) -- more fun and safer.