I know the noise you're talking about.

My mom had a '94 C220 that was noisey at idle, kinda like a fork in a garbage disposal.

There is a young kid who lives in my townhouse complex who has a C230 Kompressor (he's Chinese with parents that spoil him), and when he drives past my unit in the driveway, you can hear the difference between what a normal C220 / C230 makes and what the Kompressor's make.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".