The 2.7T is endlessly tunable and the B5 S4 is THE Audi 'stage 3' sleeper — K04s, fueling, chips routinely pushing 400+ hp on the original block. Great as a learn-on, build-it platform, but it means stock, unmodified, well-documented cars are the rarer (and more collectible) find.
The definitive Audi tuner platform — most cars are modified
Audi S4 (B5) · community-sentiment