I understand the thought, but that is actually the seam between two pieces of clear bra you are seeing, not a crack in the bumper.Sorry for the necro-reply (bringing a dead thread back to life..) but looking at your photo on a real computer where I can blow it up nice and big makes me think something is seriously wrong with your bumper:
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That really does appear as a crack. And that would explain your center panel coming loose. Perhaps try some duct tape and see if that stops the feeling of instability. Since I believe that's the side the tow hook fitting is on, could the toe-hook license plate mount have wanged the section somehow? Or directed way too much air in the area?
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Sure looks like one to me. A new bumper cover might be in order..
Seems strange that all the experts who've looked it over - overlooked something this obvious.
I've been busy collecting all of the pieces required for a third radiator install, so far not quite successfully as most retailers will not ship to my address here in Germany, which is an APO address.
I found a parts list for the kit on FCP Euro, and ordered all of the parts from a local Porsche dealer, but still am missing one critical part that I can't find the correct part number for. It's the part that clips to the bumper and secures the radiator cowl to direct the air. Also have yet to find the part number for the two nuts required to secure the bottom of the radiator to existing posts coming out of the body.
Any help in finding those two parts would be appreciated.