I applied 303 high-tech fabric guard to the upholstery, headliner, and carptes of our new Subaru. Seems to be working great. But I got some overspray on the dash and tops of doors (black plastic). This caused very faint spots that I can't seem to remove. Thought after a few applications of 303 protectant, they would be gone - but I was wrong. Also tried cleaning with my Zaino cleaner - this didn't work either. Any suggestions?