I picked up an '08 Pontiac G6 V6 DD back in July. Been very happy with it so far. However ... I've noticed that there are "shadows" of numbers and letters on the exterior of almost all the windows. I'm sure the dealership acquired it at auction and those were some type of markings to identify the car. I've tried Windex of course and Rain-X but you can still see them especially when there is a little dew on the car. Any thoughts on how to remove them? Thanks in advance for any help.