The 2008 Audi RS4 is a high-performance sedan for a street-racing enthusiast who might have bought a Mitsubishi Evo if he weren't so darned rich.

At a base price of $66,910, the RS4 is in no danger of winding up on blocks on the shady side of a trailer park - unless the park happens to border an international speedway.

The RS4 is such a rarity that you might want to look for interlopers in the German parent's gene pool. That such a wicked, wicked set of wheels could emerge from such stately heritage is worth marveling over.

Not that Audi hasn't had its share of powerful cars - and sporty ones like the inimitable TT. But the RS4 has the heart of a boy racer just looking for a challenge on some dark street in the Inland Empire.

Imagine, if you can, soaring from a dead stop to 60 mph in 4.6 seconds, then continuing to 120 mph in 16.6 seconds, finally topping out at an electronically limited speed of 155 mph. Just imagine it, but please don't try it in real life unless you are on a legitimate racetrack.

The RS4 is the kind of car that must give BMW nightmares, threatening to refute the ultimate advertising slogan. Production cars that can compete with RS4 are few and not so far between, including the most potent version of the BMW M3, the Lexus IS-F and the new Jaguar XF among the most notable.

Lexus claims identical 0-60 mph times but pours torque through an eight-speed automatic rather than the six-speed stick found on the RS4. The IS-F also carries a base sticker price about $10,000 below the Audi's.

RS4 represents an extension of the A4 family, with "RS" standing for "Renn Sport," Audi's ultimate trim level, positioned above the "S," or "Sport", line.

The current generation RS4 debuted at the North American International Auto Show in Detroit, arriving after a five-year hiatus from the first generation introduced in 1999 as an Avant wagon. The 2008 sedan became available in North America in 2007.

Audi's chief advantage against well-wheeled competition is its Quattro all-wheel-drive system, which adds a level of stability, safety and control that could represent a benchmark for the breed. The six-speed stick brings out the absolute best in the blend of power and traction, boosting the driver's ego to unseemly levels of hauteur.

Under normal driving, torque splits 40 percent to the front wheels and 60 percent to the rear. A strict diet reduces the sedan's weight to 8.7 pounds per horse.

The compact V8's direct injection technology known as FSI squirts premium unleaded directly into the combustion chamber for a better mixture of air and fuel, while cooling the process. Audi developed the process for the R8 prototype race car, a five-time winner of the 24 Hours of Le Mans endurance race.

Peak horsepower comes at 7,800 rpm with peak torque of 317 foot-pounds at 5,500 rpm. The engine delivers at least 90 percent of maximum torque at engine speeds from 2,250 to 7,600 rpm. Red line comes at the unusually high level of 8,250 rpm. All the throttle inputs are conveyed electronically, with no mechanical gadgets.

The sedan's high-performance, aluminum sport suspension includes a four-link front axle and a trapezoidal-link rear axle that provides good driver feedback, great agility and directional stability.

The 19-inch wheels are equipped with large vented disc brakes that are as large in diameter as some tires on economy cars. Stopping power is an area that the German makers seem to have mastered.

Audi's Dynamic Ride Control reduces body roll and pitch, especially during acceleration and braking. Other features included in the electronic stability program are the electronic differential lock, traction control, electronic brake force distribution, and anti-lock brakes.

As befits a car in this price range, the SR4 is well equipped, sophisticated and stylish. Muscularity is expressed through wheel arches that are flared to fit a track measuring 1.5 inches wider in front that the S4's and 1.9 inches in rear.

Other signatures include RS design bumpers with diamond-styled grille, flared side sills, rear spoiler on the trunk lid and side panels, twin-chamber exhaust system with oval tailpipes, and RS 4 badging at front and rear and on the side.

Leather-clad sport bucket seats are bolstered to keep passengers in place during hard maneuvers. Aluminum and carbon fiber materials accent the interior. Perforated leather covers the steering wheel, the gear knob and handbrake. The brake, clutch and gas pedals are made of lightweight aluminum.

While there are several attractive options for the RS4, the one you might want to consider first is a private racetrack. It would be a shame to let all that power go to waste.