I won't keep you in suspense. The gas cap tether.
Picked up a new cap/tether today at local dealer. Parts department had one in stock. $29 with tax. (0.95% -- welcome to CA!...)
Installed it myself. Oh, I checked with a tech and he walked me through the procedure. Drive a plastic rivet pin out and then remove the old tether anchor and use the old rivet and pin to secure the new tether in place.
A bit of a gotcha... Be sure to cover the drain hole in the basin. If the pin falls in to there it is lost and one needs a new rivet. I taped over the hole with masking tape, two pieces just in case. Might add the newer models have a slightly different procedure the tech covered it but I don't recall what he said now.
Anyhow, for my 2002 Boxster it almost takes longer to type in the above than it took to do the job.
With the old cap out I was able to have a close look at the old cap. The rubber seal is very cracked. Some cracks extend in from the edge almost to the point the crack is in the shiny part of the seal where it mates against the gas tank filler tube. A gas cap leak was not that far away.