Benno

I've got the headlights on my 2000 Legacy protected with soft, clear vinyl protectors(made by 3-M) which are adhered with it's own adhesive backing. I put them on several years ago. They are now starting to become discolored and somewhat opaque; cleaning them using various cleansers doesn't help. I'd like to remove them but they seem almost welded to the headlights. Is there any way to remove them without damaging the headlight surface underneath?