Over time everyone's exhaust tips get grimy and coated. The carbon buildup and discoloration start to settle in. So I grabbed one of my favorite products for cleaning them up Mother's Metal Polish. I get the paste that comes in the small can and get great results. Easy to apply with a rage and no need to let dry. Keep working the product until you start to see some discoloration in the paste and then turn to a dry part of the towel and buff out.