Audi's RS line first appeared in the 1990s in Europe with the RS2 and the RS4, both Avant wagons. These were twin turbo V6 engines with quattro all-wheel drive and were meant to be the top-line performance cars, the next level up from the S-class of cars. They were not available in the U.S. however. But with the success of the 2002 RS6, Audi decided to bring back the RS4 and bring it to the U.S. for the first time. The new Audi RS4 is just that. All new and more of a supercar than ever. Introduced at the 2006 NAIAS Auto Show, the RS4 is only offered as a sedan, though an Avant wagon and convertible are in the works. Though it's based on the new A4 platform, the RS4 is quite different once you get behind the wheel. For the first time in RS history, there is no turbo engine. The RS4 gets an innovative FSI direct fuel injection 4.2-liter, 420-hp V8 engine that hits 0-60 in 4.7 seconds. The FSI purportedly improves engine power and fuel economy at the same time. It is still all-wheel drive, but with a new and improved quattro technology and Dynamic Ride Control with a 40/60 front-to-rear torque differential, to give the RS4 the grip and handling of a rear-wheel drive racer. One of the problems with the old turbo RS4 was that its heavy weight got in the way of true performance status. With this in mind, and fully aware of its BMW M3 rival, Audi has been very weight conscious with its new RS4, giving it aluminum body parts and suspension and paring down some of the standard features found in the S4 in order to maximize engine output and road handling. On the outside, wider 19-inch wheels, fender flares, side skirts, lower ride height, huge quadruple oval pipes, and air intakes increase aerodynamics as well as distinguish it from the more staid A4 on the road. Audi can't completely give up its luxury image, and despite the paring down, the RS4 still comes well loaded with power features, power seats, a sunroof, remote locks, and parking assist. Leather sports seats have adjustable side bolsters. Clearly with the RS4, Audi is trying to find that perfect combination of personal luxury and optimum racing performance to please every facet of a driver's life -- whether it's an upscale business meeting, comfortable family trip, or the need to let loose and tear up the open road.