The C5 chassis was a revolutionary design change from the C4 and brought the styling into the modern era of Audi. Available with a twin turbo V6 and later a 4.2L V8 the A6 had plenty of go to match it's all wheel drive traction. The 2.7T engine is considered the hod rod engine of the 1999-2010 Audi era and many companies have produced and continue to produce a staggering amount of aftermarket products for this much loved engine.