1982 GLT B21Ft M46 w/overdrive

History: Purchased car with approximately 130,000. Oil cooled turbo was shot- towed it home. Replace turbo with water cooled rebuilt unit. Broken exhaust stud. Removed head. Fixed stud, milled head, lapped valves, replaced intake stem seals. Reinstalled head. Performed major service. Car ran great. My only complaint has been a surging idle.

Problem: 22,000 miles and a couple of years after rehab it has developed an intermittent problem affecting driveability. A few thousand miles ago it started running poorly upon startup. It would seem to be running on only two or three cylinders but would smooth out and be fine after running between 15 and 30 seconds (remember intermittent, sometimes all wold be fine). This has become more pronounced as of late. It also has progressed to lacking power after underway and at highway speed. It seems like a miss but it is hard to tell. It produces a subtle lurching. Again not all the time- yesterday it was running great, today the problem was as bad as it has ever been. It almost feels like the ignition timing has been retarded, but there is the associated lurching.... It takes a long time to reach its highest boost levels (half way into the yellow).

What I have done: It is difficult to figure out if I'm dealing with a fuel delivery problem or an ignition problem. I have cleaned and dielectric greased the few connections I can access (although not the ECU connectors... worth a shot???). I have replaced the plugs (NGK) and the ignition wires, cap and rotor (Bosch). I ran a can of BG44K through it. Fuses cleaned. Wiring harnass appears original and in good shape. I did replace one suspect wire to a temperature sensor in the head while it was off. I think any vacuum leaks are under control. The old plugs (Bosch Platinum) showed a rich running condition. Something I hadn't noticed before.

Anything associated with this problem sound familiar to anyone? Or perhaps suggestions to further diagnose the problem?? I appreciate any input. Thanks

Randy