The black trim on the Msport line has been discoloring for awhile now, fortunately it's fairly easy to clean.
SITUATION
The optional glossy black Shadowline exterior trim may become discolored.
CAUSE
Analysis has determined that the discoloration is due to a film deposited on the trim which distorts the light reflecting off the trim. These deposits may come from car washes, hard water, or other environmental conditions.
CORRECTION
Deposits that cause the discoloration can be easily removed by polishing with a quality swirl removing polish, such as Meguiars #9.
Note: The glossy black trim pieces are anodized, not painted, and the discoloration does not mean that the surface has been damaged. Therefore, the trim pieces should not be replaced for this complaint.
http://www.1addicts.com/forums/showthread.php?t=215977