My '98 has perma-stain on the exhaust side of the green belly pan. Nothing will clean it now, I've tried everyting! The stain has worked its way into the plastic. I am thinking about buying some new green side pans, but if I do, is there anything that can prevent the exhaust stain from happenign again? Something to spray on, perhaps, that would help prevent the exhaust soot build-up?