Not content to leave well enough alone, Audi may import this ultrahigh-performance version of the A4 sedan next year. Unlike the potent S4 which uses a larger V8 for power, the RS4 may revert back to twin turbochargers hooked to a 3.0-liter V6. Spy photos of a prototype circling Germany's famous Nurburgring test track show a car with a slightly lowered stance and exaggerated bodywork similar to the midsize RS6. If it does in fact show up on American shores, don't expect it until next spring at the earliest.