I am looking to BUY a 928 S4, 1988-1991, less than 70K miles. Is there a forum for this?

The GTS used two different Cup wheels. The 93 and early 94's had what is commonly referred to as Cup I. The late 94's and all 95's had the 993 Cup wheel, commonly referred to as the Cup II. With both you will be looking for 928 fitments, which are 17x7.5 ET65mm front and 17x9 ET55 rear. They will fit your S4 just fine. Click here for more:

928registry.928oc.org/928-resources/perf...cosmetic/wheel-guide

Congrats a your find Bob.
As martin said, we look forward to seeing pictures.
Start your own page in the my 928 area where everyone has posted about their car.
Again congrats and many happy years driving

928mac wrote: Start your own page in the my 928 area where everyone has posted about their car.

That would be the 'OC Member Car Profiles ' sub-forum.

Also, be sure to register your car in the 928 Registry