I have a Porshe 944 and I had illegal tint to remove. My friend (shop foreman for Mercedes) told me to use simple green (spray bottle 3/4 water to 1/4 simple green).

Park car directly in the hot sun.

Spray simple green on the inside of the window (make sure all windows are up).

Place saran wrap (over the simple green spray) on the windows and make sure it sticks. Cover the whole surface. Wait 2 hours or so.

In one instance when I went out to the hatchback, the tint had fallen off of the middle of the window.

Works like mad.