See if you can find some Citrol. I had a nos nova hood lip molding that had been in the package since I was 18. The clear part of the wraper had seemed to etch itself into the molding. I tried thinner, goofoff, even the rubbing compound. I pretty much figured that I'd send it out to my polish guy to see what he could do with it. He got out a spray can of Citrol, sprayed it on, and the stuff came right off. It's environmentally friendly, and smells like oranges.Works great.
I had tried the adhesive remover also.