If Mercedes is full of shit then Car&Driver must be too. Here is a cut abd paste from an article in Car & Drivers web site and magazine discussing the light weight and 349hp Mercedes AMG C32 and SLK 32...

Whereas the C43 relied on cubic inches for its grunt the C32 relies on the heavy breathing induced by a belt-driven supercharger. AMG cites the advantages of a more compact engine that allows better weight distribution and because its shorter improved behavior in a crash. The supercharger (a Japanese IHI helical unit rather than the Roots type employed on Mercedes four-cylinder Kompressor engines) only operates when the driver demands acceleration and then at a pressure of up to 14.5 psi. Its seamless operation means youre never aware of its cutting in only of instant power from just a few hundred rpm above idle

and here is the link to the article...
http://www.caranddriver.com/xp/Caranddriver/previews/2001/June/200106_preview_benzs.xml