The heart of the ML55K is the capable 607-horsepower engine. The added power comes courtesy of a Kleemann-engineered kompressor system designed to optimize every last horsepower, without compromising the elegance expected in a Mercedes-Benz. Kleemann calls it Comfort Power, and, in our short but thorough evaluation, we were impressed. The ML55K didn't exhibit the lack of powertrain refinement found so often in tuner vehicles. As we walked away from the ML55K, we were convinced that if Mercedes-Benz or AMG wanted to extend the abilities of the current or future M-Class, they had a clear target to aim for in the ML55K.

The Kleemann ML55K benefited from a few other strategic improvements. Toyo supplied the tires, 295/40R20 Proxes S/Ts, mounted on Kleemann's own 20x9.5-inch wheels. The chassis was lowered two inches with Kleemann's M-Class lowering springs. To slow the ML55K's three tons of moving mass, a set of Kleemann KB 4 brakes were installed with six-piston calipers up front and four-piston units in the rear. The 15-inch front rotors (13.7 rear) were cross-drilled to maximize cooling. Inside, the world-record ML55K was essentially stock, save for the specialized handicapped controls installed for Jason Watt (who was severely injured in a motorcycle accident in 1999).

When we visited the Kleemann facilities outside of Copenhagen, we saw a half-dozen Mercedes-Benz sedans under construction, each in the process of receiving a custom leather interior. Kleemann representatives explained that a customer could personalize an interior in any trim available. The Kleemann signature combination of leather and Alcantara is mated to the customer's choice of stitching pattern, resulting in a one-of-a-kind interior. Kleemann also offers a variety of wood and carbon-fiber accents.

As it turned out, we didn't need to fly all the way to Copenhagen to sample Kleemann's charms, since a U.S. subsidiary has been established in Colorado Springs, Colorado. Kleemann USA (719/473-6441; www.kleemann-usa.com) can personalize any current Mercedes-Benz vehicle using a host of Kleemann-engineered components, from vehicles equipped with the 3.2-liter V-6 up to the 6.0-liter V-12 models. If you currently own an ML55 and want to upgrade it to ML55K specs, Brandon Grantham at Kleemann USA says the world-record ML55K can be duplicated in a U.S.-legal and certified version for approximately $34,600 above the cost of the donor M-Class, labor included. Certainly not cheap, but you'll get an incredibly fast vehicle.

In the years since its introduction (a replacement model is expected for the '05 model year), the M-Class has become very popular, selling 60,000 units annually. While it was considered the class leader when Mercedes-Benz introduced in '98, it's been clearly eclipsed by later introductions like the BMW X5 and the Porsche Cayenne. While these competitors may boast of a more contemporary chassis with additional levels of refinement, neither can make the claim now being the world's fastest SUV. And for some, that's all that matters.