I tried Chevron Techron on the '91, didn't change it. The RedLine did.
http://www.germanautoparts.com/Chemicals/Fuel%20additives/Redline
My car never had a bad fuel problem, it just was something that started to develop and get worse when it was about 3years old, over several thousand miles. It didn't have a chance to get stale fuel, was 5years old and 120,000 or 130,000miles when I sold her (click on avatar, 1996 photo).