I think cleaning them is fruitless....it is a common Ford problem, I have given up trying to figure it out, and am going to buy new lights.....my g/f has a 97 Mustang with the same problem.

1996 Contour GL AT, 2.5 V6 No mods, rollin on 14's with hubcaps, 116,000 miles, and still havent been beaten by a ricer.