[carsngolf]

Hi Otto,
That's a tough one. That plastic cover is evil. It is made of a material which does not age well. I had the same problem and finally just broke it loose as best I could. Once I got it out, I tried to clean it but it was not possible. Short of creating a vacuum mold to recreate the piece, I don't think there's any way it can be made to look good. Please keep us up to date on your progress or lack of it.
Good Luck.
Jerry Weiland