A subset of CLK55s wear kompressor/Kleemann/custom supercharger builds with cams, ported heads and tunes making 440-500+ rwhp. Knowledgeable commenters caution that the NA M113 uses high-compression non-forged pistons unlike the factory 9:1 forged M113k, so boosting the base engine 'is asking a lot' without careful tuning.
Supercharged CLK55 builds and the M113 vs M113k question
Mercedes-Benz CLK55/CLK63 AMG (C209) · mechanical