Take a normaly aspirated SLK 55 AMG and let
Kleemann put a kompressor (supercharger) on it, and you have more torque than an Enzo. The SLR engine is also a 5.5 V8 with a kompressor.
But, the SLK is heavier than the Enzo standard, and the standard SLR engine has less power, but more torque.
Maybe the SLK has been lightened? Or the Enzo driver is changing gears too soon?
Since the supercharged engine has more torque, it's no surprise that it will beat the less torque-y car when driving at low rpms. The Enzo engine needs to be close to 8k rpms.
EDIT:
Danny: I like your thinking. A sleeper like that would be cool. My idea of the perfect sleeper is a tuned Audi RS Avant with the RS badges removed and side mirrors without the chrome. Maybe even take off the RS "bodykit" for a bog-standard one, and put some 16" wheels on it.
I just don't like the look of the front of the SLK. And no matter how many HP you put in the SLK, an Enzo would still kill the SLK at the first sight of a bend. And the SLR - well, for me a supercar needs a engine in the middle, anything else just isn't very "super".