I bought a pearl white '95 SC rear bumper a few months back which was in great condition save for some light scratches and blemishes. I washed it using Dawn to strip any waxes remaining on the bumper and clayed the surface to get rid of the majority of scratches and paint rubs from other vehicles. Here's the hitch: There is a lot of bumpy, tar-like oily grime on the sides where the bumper would meet the rear wheel well and for the life of me I can't remove the stuff. Tarminator and a lot of elbow grease have done nothing. Can anybody recommend something else to try?