EEC IV Trouble Shooting

My vehicle is only "nominally" a Mustang. It is actually a London Coach -- a london taxi Carbodies chassis imported into the US minus engine /transmission and then fitted with a Ford 2.3L engine and C3 automatic. About 150 built before the company went out of business. It is 1985 EEC IV compliant and I buy engine parts for it as a 1985 Mustang. 42,000 miles on the clock.

My immediate problem -- warm summer day with engine warmed up, picked up the throttle coming out of a tight right turn and the engine began choking, sputtering, running ragged, tried to die. Coaxing it home I found I could get it to run ok at 2/3 to WOT after I got it past the unburned fuel. All this very sudden, no issues like this before.

So far -- have replaced plugs, coil, TFI module, and voltage regulator, and pulled the connectors on various sensors just to check. Sometimes car will start and run normally after a day's rest, sometimes not, will always begin to choke, sputter, misfire after warm up and will also always run ok at high / full throttle; open loop. Old plugs were firing clean.

What confuses me most is that if I pull the connector on the external voltage regulator and take the charging system out of the circuit, the car runs just fine. Base engine management / open loop mode I'm sure, but why I haven't a clue. Resistance and voltage checks indicate the alternator appears to be ok.

Also, as you might imagine I'm dealing with much non-standard wiring and I think I've just located the PCM way up under the dash

Any help / assistance / guidance you can provide would be MOST welcome.

-- Don