Audi S4
Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential (ATB) was used on vehicles equipped with manual transmissions, while a transfer box based system was used on vehicles equipped with an automatic transmission.
Audi A4
In 2007 Audi introduced a version of the B7 named the 'Special Edition', which built on the S-Line specification and also included the black optics pack, the RS4 style 8J X 18 '7-arm double spoke' design alloy wheels, Two-tone Graphite/Black Volterra leather, 3-spoke sports leather/Alcantara multi-function steering wheel with gear knob and hand brake
handle in Alcantara with silver stitching, ventilated cross-drilled front disc-brakes, black tailpipes and black roof rails (Avant model only). It also had a power increase of 20 PS, giving an output of 220 PS on the 2.0T model.