I hate to sound clueless, but I saw something today on a yellow XF Roadster (when it passed me on the highway) that I've never noticed before. It had 4 "quarter" sized circles positioned, or spaced equally, across the middle section of the rear bumper. They looked very much like the "pressed in" circles that you see on the rear bumpers of newer, full size Cadillac's. Does anybody know what they are? Is it a plug that pops out to gain access to something hidden under the bumper or what? It looked as though it was something that came from the factory, and not added later. If all Roadsters have these, and I simply never noticed them before, boy am I going to feel stupid. So be gentle, OK?...Thanks.