I had a similiar problem on an 96 850 NA engine this spring. I kept getting a long term FT error (are you using Alex Peper's software?) but my other code was "system too rich". To make a verrrrrry long story short, the O2 sensors were wrong. I changed them myself. As they were new, they were overlooked by my regular mechanic as a source of the problem. After he tried numerous other things w/o success, I finally took it to a different indy who found the problem right off. Apparently, many mechanics and o2 sensor vendors have charts showing the wrong sensor number for that engine. He changed them (again) and presto, the car has been perfect since. Won't go into how much this episode cost me. Just a thought.

bl