And the same here with my '90 765T, B230FI. It's resting at the moment
because I'm tired of chasing down every last little thing that could be
wrong with it and still not finding a solution. The idle problem got
steadily worse and the car is now undriveable. It's also running extremely
rich. Here's what I've done so far:
  New air filter/fuel filter. Cleaned out IAC. Checked and adjusted
throttle & switch. Cleaned inlet galleries etc. Checked AMM. Checked all
vacuum lines etc. for leaks. Replaced inlet manifold gasket. Pulled all
possible relays, cleaned points, checked continuity of coils, checked
circuit boards. Replaced coolant temp sensor under inlet runner 3. Replaced
O2 sensor. Pulled all related connectors, cleaned with contact cleaner,
reassembled with silicone grease (except O2 sensor leads -- they're best
left bare). Replaced spark plugs and leads. Cleaned injectors, tested for
leaks and spray pattern, reassembled with new seals. Cleaned and reassembled
all ground contacts. Bench tested fuel pressure control unit and checked
fuel line pressures. Replaced rusty section of fuel return line and checked
for unrestricted return flow. Checked rpm sensor for continuity (couldn't
get the thing out but it looks okay). Tore out hair. Said rude words.
   And I've probably done other stuff that I don't remember now.

Is there anything I've overlooked? Is there anything you guys have done
that's made the slightest difference?

I'd be really, really interested ...

Pete (fP)