I'm sure most, if not all of the roadster owners have a fading problem with the tape strip under the rear seal on the deck. I've found a decent, if temporary solution to this.

Before

1. Wash well with a degreaser. Dawn dishsoap works well.
2. With a DA polisher (Porter Cable 7424 for example) or by hand, apply a mildly abrasive paint cleaner. I have used Meguiars Deep Crystal Paint cleaner and Meguiars SwirlX with similar results. Just follow the directions on the bottle. Notice the results
   This 1/2 done. Just cleaned-no wax.
3. Apply protective coating. I use Meguiars NXT 2.0.

I did this last 6 months ago and it only recently started to go 2 tone on me.

Hope this helps.

P.S. Mike-in-Orange was a little surprised this works, but said stranger things have been reported.