I've got some dried-on sticker residue on my P4 shell that I have to remove first before I put on a new registration sticker. There's plenty of products out there to remove sticker residue, but many of them will dull the finish of polished plastic surfaces, like the P4 shell. I know that to be true because it's happened to me before on some different polished plastics. I'd appreciate suggestions from someone who has actually removed sticker residue from a P4 shell without dulling or discoloring the polished surface. Thanks.