Try the black again stuff from meguires, don't recall it's exact name. The top is not really paint, is an odd texture surface. I cleaned up one targa top a couple yrs back with, mineral spirits (testspot first, never know if someone painted it) then used a coating of the black trim bumper stuff, came out looking great. Mineral spirits because someone painted it and it was going gummy and pealing in spots... Nothing to lose. The spirits didn't harm the top, it was a 328. But test first if you go that route.