I have a tip for anyone who has been trying to clean the black carbon build-up off of their chrome exhaust tips (especially if you don't run cats): take your tips off and put them in a bucket with CLR (bathroom cleaner) and hot water and let them sit for about 15 minutes. Take them out and scrub them with aluminum foil (will not scratch chrome) and then your tips are looking almost new again. Do yourself a favor and do this before it gets too bad or it is a PIA.