Headlight Housings

The housing or lens??? If its the lens, you can wet sand it with a fine grit sand paper (like around 1500 or more) and then buff it out. I have heard lots of theories about why they turn yellow but I will have to go with my buddy who is a quality engineer at the Sylvania Plant that makes the OEM housings. He says it is due to the old process of making them for the older model cars and sadly the repro's are made the same way. He could go into depth on it about the whole process but I can't. That is why you only get a year warranty.

Try wetsanding them. I thought that my headlights were turning yellow from the inside too, so I bought a set of ultra clears. But once I wetsanded the stockers they turned out looking brand new.