I recently removed my 3.9 MPI side badges. The only advice I can give is to go very slowly with removing the sticky stuff. Even then, I have a slight darkened mark around where the badges used to be which no amount of rubbing will get rid of, but it looks better than it used to.
Jack Travis, E-Series Acting President
1989 Ford Fairmont Ghia turbo/GL replica (underway)
1994 Eunos 800M
1990 Ford Laser S