Thanks guys! Yes, Exclusive Motorcars was a RUF dealer (sales brochure is listed on EBay. See link below). Perfect Power is probably the Chicago-area dealer you referred to onboost. Perfect Power performed the 1988 work on my car. Still a successful and thriving business doing very impressive work on 911s. Sol, the owner, helped educate me on my car. Now hoping someone can provide color/history on the overall US RUF program at that time. Thanks again!
https://www.ebay.com/itm/Porsche-911-CARRERA-RUF-CTR-YELLOWBIRD-Sales-Brochure-Origianl-1980s-Literature-/254587808824?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=711-127632-2357-0