I have seen a few ads for "xenon" bulbs. Will those bulbs, if rated at 55W (like stock bulbs) cause the plastic headlight cover to turn yellow? If so which part of the cover turns yellow? I always think the lens only turn yellow if the bulbs are rated much higher than 55W. I am wanting to use regular Sylvania Silverstar bulbs but I'm curious about those "xenon" bulbs. Any thoughts?