Recently purchased 2006 S type R faded /scratched headlight and fog light covers. Tried turtle wax chrome polish on the plastic...worked great. took out most scratches. finished with Maguiar's #10 plastic polish and a simple buffer pad over the top of a 5" sanding disk look like new ... Give it a try...

 

Good work. You need to deal them to last or you will need to polish couple times a year.

I use the 3m headlight restore kit. Works like a champ. As a matter of fact a buddies son is on his way now to restore his pick up headlights.

 

When I bought my car, the headlights were badly discoloured yellowy. They had also been covered in what looked like a sealant or laquer. I tried the cheap methods such as toothpaste to no avail. I bought the Maguires polishing kit, using all 3 grades of wet and dry paper and the polishing compound. They came up almost as good as new. Recently had the whole car mopped and polished and this just added the finishing touch.

 

The restoring kits have a UV resistant laquer that is applied on last.
No need to to keep polishing.
I did mine 2 years ago and they are still good.
Well worth the money.