actually i think he might be talking about something else. I had to get mine replaced under warranty b/c the casing was shattering. It looked like fiberglass shattering..hundreds of tiny x's on the casing, kinda rough. it wasnt a yellowing or fog, it literally looked like the platic was splintering apart. I dunno if thats what it is or not man, but they will replace it under warranty if you have it it still.
yeah what green said, lights can come bad from the start, just bad mold, but on 94-98 and maybe 99's, you can use polish, I have found a web page that shows how to wet sand the headlight and bring it back out to nice smooth and clear. I will try to find it once more.