The 928 GTS has a rear trim "reflector strip" that is fitted by two tabs that lock behind the taillight units.
Regretfully this trim bends due to the setup two sorts of plastic glued together. It is said that even the new ones from factory have this, and the 911's seem to be suffering from similar problems. The Velcro that is supposed to fix the trim to the rear PU bumper is not able to hold it and lets go. After a while the trim is bent so bent that it will not stick and pops up showing annoying the owner.
This is what I did....
Original idea from Roger Tyson. I modified the solution a bit, not using the elevator bolts Roger mentioned.
The problem of the 'bowed out' center reflector strip is due to two things in
my opinion. The dissimilar plastics used in the inner and outer halves of the
strip cause the strip to warp over time. The velcro attachments weaken, allowing
the strip to bow out even further. By the time it becomes obvious that there's a
problem, the strip has bowed out so much that the velcro attachments do not have
enough 'grip' to restrain it in the flat position.
Here's the easy way to fix it.
First, remove the reflective strip. To do so, remove the tool kit to gain access to the rear light assemblies.
Each light has a large aluminum hex bolt that secures the light in place. Loosen by hand and remove the hex bolt - it should be just finger-tight. You will see that the bolt has a secondary locknut that is used to set the inset depth of the light assembly.
Once the hex bolt is removed, the light assembly can be swung out and removed.
The reflective strip has tabs on either end that sit behind the light assemblies, thus the reason to remove the lights first.
Pull the reflective strip off. It is attached at each and and in the middle by heavy-duty hook-and-loop fasteners (velcro). Trying to replace this with new velcro will not work, as the outward bending force of the now slightly warped reflective strip is stronger than the grip of any velcro material available. Trust me on this one - I first tried several different types, including super-duper marine velcro that is pretty much the same as the original stuff used by Porsche. I even tried using it along the entire length of the strip. No dice.
You will want to use heavy-duty body panel tape such as the stuff by 3M - found at Pep Boys, etc.
Get the wide 7/8" stuff like this:
A 36" roll of the stuff costs around $12.00 (not the $40+ indicated in that link)
Before you get started, you might want to give the reflective strip an good polishing with some plastic polish, available at any auto parts store. This will remove most scratches and hazing and will make the strip smooth and shiny like new.
Step 1: Remove the original velcro pieces from the back side of the reflector strip AS WELL AS the velcro pieces on the rear body panel. It may take a bit of scraping to get it all off.
Step 2: With some medium sandpaper, rough up the entire backside of the reflective strip AS WELL AS the painted body panel it attaches to. Yes, I know it doesn't seem right sanding that nice shiny paint under there, but once the strip is back in place you'll never see it.
Step 3: Wipe the back side of the strip and the body panel with isopropyl alcohol to make sure it's real clean and let dry thoroughly.
Step 4: Dry fit the strip so you have a good idea of how it will be put in place once the panel tape is on. The reflective strip fits within the bumper indent with very little up/down or lateral movement, so it's pretty easy to get proper placement.
Step 5: Cut two (2) strips of the body panel tape that are almost the length of the reflective strip, leaving them 1 inch short from each end of the strip.
Step 6: Apply the two lengths of panel tape along the length of the reflective strip, spacing them evenly top to bottom, about 1/2" in from the edge. Push the tape down securely along the length, running your hand along the plastic release liner.
Step 7: Once you are satisfied that the tape is securely stuck to the reflector strip, carefully remove the release liner. Pull it back at a sharp angle to prevent pulling the tape off the reflective strip.
Step 8: Place the reflective strip against the body panel, trying to get the middle section to stick first (slightly bowing the strip inward) then working out towards the ends. Using a soft cotton cloth, apply firm pressure along the length of the strip to ensure good adhesion along the length of the strip.
Step 9: Reinstall the light assemblies, adjusting the set nut on the hex bolt as necessary to achieve proper flush mounting of the lens relative to the body.