350 is too hot.

My quote from Anita's link:

"Locate an oven make sure that there is only one rack in oven and that it is on one of the lowest tracks in the oven. Test fit the cookie sheet/towel/1 headlight into your oven to make sure no metal is going to touch the headlight. Then turn your oven on and set the Temperature to 200 degrees exactly. Get a large cookie sheet, and cover the top of the cookie sheet with a damp towel. Then place your headlight onto the towel which is on top of the cookie sheet. Place headlight into oven and let it sit in there for 5 to 6 minutes. I would suggest wearing gloves from here on out. Remove cookie sheet and use a flat screwdriver and start slowly making your way around the headlight loosening the glue in between the clear plastic cover and the black plastic base of the headlight. Once you have gone all the way around once prying and turning the screwdriver start to pull the headlight apart with your hands. If you start to feel it coming loose keep going. If not place headlight back onto cookie sheet and place in oven for another 2 to 3 minutes, then try and pull apart again. Eventually it will break loose."