This is correct. Several MB C32/SLK32 as well as C55 owners have experienced this. The squeak is indeed the clutch on the blower. My SRT does this as well.

If these intercooler systems weren't so problematic it would be nice if we could do away with that clutch altogether.

The attached screen shot is from C32life where they say you can tighten the clutch assembly. I haven't done this yet.