You could try Mr. Clean Magic Eraser--but proceed with caution. It's basically an abrasive foam brick (this was discussed previously and I think that this was the general consensus) that will clean just about anything off of anything. It's really an excellent product, provided you know what you're doing. I've used it successfully on trim before--with great results too--but it could easily strip a layer of plastic and make you long for a polish stain instead. It will damage your paint without hesitation, so be very careful to not let it touch anything you don't want exfoliated. Go gently.
I actually used it today on a '93 integra i just bought -- the previous owner did one too many terrible waxing jobs and the trim was riddled with wax smears. The Magic Eraser took care of that wonderfully, and once I followed it up with PB's Trim Restorer, it looked like new.