The gray plastic on the bottom of the rear bumper where it says "GTO"--should I wax it or not? I realize it's painted, but because of the rough texture relative to the smooth basecoat/clearcoat on the rest of the bumper, I'm not sure exactly what I'm dealing with. Repeated washing seems to have left this valance area kinda milky-looking in spots. I'm assuming that since this thing is painted, a plastic treatment like you'd use on the windshield wiper surround would be a bad idea. Anybody know if it's okay to just go ahead and wax it?