This is probably the fastest Audi S4 in the world. Owned by USP Motorsports, this Audi S4 is powered by a 2.7-liter twin-turbo engine taken from a VW VR6, which has been tuned to output more than 800 hp at the wheels. USP Motorsports' S4 is also equipped with a Haltech engine management system. The B5 Audi managed to run the quarter mile in 9:61 on E85 biofuel.