The MTM Audi S4 Clubsport shakes as the racing clutch stalks the bite point, the whole car begging for that extra millimeter of release. And when it comes, this thinly-disguised racing car bites into the middle distance, like a crazed dog fed on crack cocaine, raw meat and horror flicks.

This car was a big box, once a refined mode of transport with a fair turn of speed, the docile family pet. But MTM has turned it into a killer; the last word in control has become a dark, violent sociopath. As every gear slots home on the short-shift box, the driveline shunts, trying to twist the whole car, and, as the needle breaks the 3000-rpm mark, a rorty mechanical crescendo of a hardcore box, supercharger whine and one of the most aggressively tuned exhausts (ever) tries to blast out my eardrums.

A supercharger lies at the heart of this transformation, boosting the 4.2-liter V8's power from an effective yet detached 344 bhp into an altogether more intense 450 bhp. More importantly, the wagon with serious attitude now has 413 lb-ft of torque to blast through all four wheels. That can leave tarmac making emotional television appeals for U.N. intervention.

Audi has followed BMW towards a V10 configuration for its big-power cars, but there's something to be said for a supercharged V8. Blessed with near-stupid amounts of torque, it doesn't need wringing out like a damp cloth to tap into the acceleration. And while ten cylinders may sound a little more cultured, some would rather sacrifice their first-born than the right to drive a muscular V8. It happens in Europe too, so it's far from just an American love affair.

This newly-charged Audi will hit 62 mph in 4.8 seconds and top out just shy of 190 mph. And those numbers could be conservative. One German car magazine got to 62 mph in 4.1 seconds when they strapped on the timing gear. As I hang on to the wheel and try to avoid hammering into the limiter, this feels closer to the truth.

In-gear acceleration is similarly ballistic. This car will just dig in and fly past anything in its path; there's almost nothing on this planet that will beat it on a winding road. Purists still mock four-wheel drive, but it has now developed to the point where Ferraris would be mere specks in the mirror on difficult tarmac. It's sold as a track and fast road car. You can imagine the look on the F430 driver's face as this goes around the outside on track day.

And for a car that weighs more or less same as the 3,800-pound daily driver rolling off the Ingolstadt production line, it deserves more than kudos, more like a standing ovation. There have been a few weight-saving measures, including lightweight axles and that artfully produced carbon-fiber bonnet with added vents. Then there's the stripped-out racecar interior. Recaro seats (just two of them) and a rollcage aren't an obvious marriage for the S4, even though it is undoubtedly quick in its own right. MTM has been tooling up the Avant for many a year, though, and knows just how serious the demand for tricked-up Audis has become.

The racing wagon has become its calling card, along with the Bimoto TT, and boss Mayer has a habit of demolishing much more obvious sports cars at the Tuner Grand Prix each year-much to the delight of the crowds who appreciate the sight of an RS6 drifting through bends like a NASCAR on wrecked tires. This goes well beyond anything you'd ever need for the public road. It's not just the almighty helping of power and torque; this car has been honed to the limits of legality. Those massive fins on the rear aren't there for dramatic effect, or even aerodynamics. They ensure the wheels don't protrude from the bodywork, and get around the legal implications of the massive footprint and two-inch wider rear track. So there's room to strap on 9.5x19-inch MTM Bimoto rims bearing super-sticky Michelin Pilot Cup Sport rubber. You'd have to be a maniac to lose this car on the public road. Trying to provoke it provides just another insight into its depth of talent.

A new independent wishbone suspension and a beefed up anti-roll bar at the rear combine with a lightweight front axle and anti-roll bar. The suspension is completely adjustable too, so it can truly scrape the ground if you want to blitz the on-track competition before giving your spine a fighting chance on the way home.

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