In the NA, the TPS consists of two switches, one closes at Idle and the other closes at WOT. My guess is one of your switches in the TPS is broke, and the DME is bring told that you are always in one mode (say idle) and the DME is using the incorrect fuel map when you are not at idle. It is easy to check the TPS but it is even easier to replace it. I bet it has a few years and miles under its belt.
With the TPS unplug, the DME is alway thinking you are somewere between idle and WOT...and I bet you are most of the time.
The TPS disables the O2 sensor at WOT. Richer mix. You are getting a lean condition for some reason. Perhaps a vacuum leak after the throttle valve, a messed up AFS or one of the temp sensors is out of spec.
83 944 = It's NOT a 'real' Porsche -- Its Better!!!!
When was the last time you changed your timing and balance belts
and/or cam chain and tensioner?
I'm betting the harness is burned through someplace. Those things get very brittle - especially the routing directly over the head / upper balance shaft housing. I'd check that area for breaks / burnthrough. Maybe it's an easy fix. In any case, I'd recommend some sort of thermal wrap on the harness once it's back together - which reminds me I want to do that on mine. BTW I don't have spare DME relay either; sorry I forgot to respond sooner. . .