I can't imagine you'd get alot of windnoise from the miror. That would be a major design flaw and MB tests those things thoroughly. The mirrors on my 420SEL are less aerodynamic than yours. Try putting some electrical or masking tape (something that won't leave a residue) over the gaps in the door of your car near the mirror. Cover 6 inch areas at a time and test drive. If at any time the noise does not appear than you have found the problem. These is a tedious process, but if all the seals look fine I can't think of another way to find the source of the noise.