JB 911

Hmmm... from reading your post I'm thinking the turbos are different, Porsche ran some different, or some cars POs ran them different. Here is a pic of the routing of my antenna cable up to the booster of which from my records is the original booster. The large oval is where the booster lives, the smaller ovals are the plastic ties (just inside the sheet metal) There are no other wires along the route mine went. There was zero access to mine thru the glove box. I tried, I removed it completely. It was a waste of time. Airbags and all kinds of other stuff in the way. I did not try removing the hood or cowling, but that seems like a lot of work. THe dash covers pretty simple, 9 screws, and a 10mm nut behind the clock, all done from the sitting position Yours has to be different???

Cannonball

Yes mine is different! My harness is located to the right above the radio and attached to the cowl in two places before it goes thru the cowl grommet and then lays in three attachment clips heading to the right fender where the booster is mounted to a stud behind the right hood hinge and strut ros. the booster antenna wire then feeds back thru the dash wall under the windshield there it attaches at a different grommet point.
Now reading your post makes me think that some cars were just wired differently or perhaps harnesses were different. And this may also be why this issue only arises on some vehicles and not others.