well, it appears that it was in the MAP system

I bought a new MAP, new hard vacuum line and rubber vac connectors; also sprayed the electrical connector with cleaner and then WD40.

so far, so good

Just throwing out some ideas. Basics first.....

If it's running over-rich when cold, it could be an issue with the coolant temp sensor. This link to the 700/900 FAQ will provide the expected temp vs resistance values:

https://www.brickboard.com/FAQ/700-900/EngineSensors.htm

If you have a Regina system it could be an issue with the intake air temp sensor although I believe a failure of that sensor is rare.

Also, if it's a Regina, you might want to pull the coil/power stage apart and clean all the mating surfaces and internal connections - pretty straight forward disassembly/reassembly.

Could also be a problem in the distributor like trapped moisture or corrosion.

If you have a timing light, connect it and see if there are "skips" in the strobe when it's running rough.

Are you getting any fault codes in the OBD?

What kind of spark plugs are you running? Are they standard copper cores or the latest high dollar "designer" plugs that the chain store auto parts places want to pawn off on you?

How's the compression when the car is cold?

--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Dear GAcyclops,

Hope you're well. Any OBD Codes? When was the engine coolant temperature (ECT) sensor - that which provides a temperature input to the engine control module - last replaced. This sensor's signal allows the fuel/air mixture to be adjusted, so the engine is not supplied with over-rich mixture, once the engine is "warm".

It is possible that when doing the described repairs, the ECT's connector - beneath the intake manifold's third runner (closer to the firewall) - was disconnected or damaged, so check that first.

Hope this helps.

Yours faithfully,

Spook