I would think if your problem is only ever in the first minute of running, that it would be fuel related; any electrical intermittent would likely be less predictable. Since a higher percentage of fuel is required on startup, and the 1986 has no cold start injector, I would think that:
a) your Engine Coolant Temperature sensor is not informing the ECU that the temperature conditions require more fuel; or
b) you have a vacuum leak after the AMM, so the mixture is lean, which is more of an issue when the engine is colder, and needs the richer mixture most.

Verifying the ECT is best done right at the ECU in the passenger side panel, where you can verify its wiring also. You can:
1) verify the temperature/resistance relationship. This can only be done if the connector is pulled. Bentley has a graph, or there's a chart at http://www.brickboard.com/FAQ/700-900/EngineSensors.htm#EngineTemperatureSensors
2) or you can read voltage while connected (see same page in FAQ).

For vacuum leaks, I think the best suggestion I've seen is to use a propane torch (un-lit) at a very low setting, with a rubber tube connected to it to introduce extra fuel to expected vacuum leak points. Block the fan air from disturbing the test, and see if seeping this extra fuel at various points (along air intake path, past AMM; injector seals, etc.) causes the engine idle to increase. If so, you've found a vacuum leak.