My 98 STX has had one headlight unit replaced at one time, and the other original, and yellowing badly. Yesterday, I tried to clean the faded one. Toothpaste barely did anything, so I, on a whim decided to use Comet cleanser. I mixed some Comet, and water to form a paste, and started to polish the light. The paste started working instantly, and as it was drying, I just added a bit of water to rag to thin the paste, and kept polishing. Added a little water a couple of times to the rag to thin the paste more, and more until the light was perfectly clean. Looks brand new now!! Worked like a charm, and only took a few minutes!

 

 

sounds a little abrasive, hopefully you followed up with some sort of protectant

 

The best thing to finish it up with is PlastX - and you are committed to continual use once they get that bad.