I just got some of the 3M plastic cleaner/polish and it worked wonders. I tried using one of those headlamp restoring kits but that screwed it up cause you had to sand it down and such and though the yellowing was gone the headlight was cloudy from the high grit paper.

Anyway, I wasn't pleased but I was waiting for the 3M stuff to arrive, well it did today and I applied it to the headlight and worked it in really good and it took away all the scuffs from the sandpaper and it looks brand spanking new. It looked so good that I had to use the cleaner and polish on the other headlamp because it looked like junk compared to the reworked one.