MMMm ive got the same problem, my deflectors had been doing my head in, they were starting creak when I reached speeds in excess of 70mph but would not have planned on removing them by leaning against them to clean my alloys and snap a chunk off. Both have been peeled away leaving the grey sh*ty residue. The lads seem to have the ideas, let me know how you go, I'll probably go for one of the safe chemical options which has been suggested.