Mine is doing the same thing, slight discoloration on the left cylinder. It's got about 6,000 miles now, but I noticed the color starting at about 4,000. I'll probably try one of the products Dog mentioned before going to the dealer. I'm not sure it's really all that important. Incidentally, I think J&P or maybe Dennis Kirk sell good quality chrome outer shields that bolt over exhaust pipes. That might be a way to permanently make this a non-issue.
