Ah, this is the project I've been working on for the past week..
After trying practically everything on the market that claimed to actually do it (but they don't), I heard that Simple Green would do it - And it does. I use Simple Green, let it soak, scrub the hell out of it, and then clean it off with water and finish up with a coat of "Back to Black". Leaves a mess on the rest of the car, so you might want to try masking off the paint with tape or something. Good luck!
