I drive an 09 Mazdaspeed3 and the paint is a nice white pearl. but as with some performance cars and white paint, the bumper near the exhaust gets stained from the amount of exhaust emissions. It's a bad picture cause it's been raining today but you get the general idea. Any suggestions? I've tried to use some elbow grease when washing with microfiber and mguires wax/wash compound. I have scratch x, and some wax, but havent tried them yet.