I had a siilar problem when my darn T Handle valve cover bolts did what my husband said they would do. Needless to say, they are in the garbage now. I have TTI headers and they said to first try soap and water with a terry cloth towel and scrub the heck out of them. If that didn't work they said to use an organic orange all purpose cleaner. I used 409 orange. It took a lot of the stains out, but they are still there. Hopefully father time will help. CP, brake clean wont mess up the ceramic coating? I might have to try that, but I am afraid.