[Excaliber]

I wonder about the timing of WHEN the EEC starts to read the O2 sensor, might be soon enough to be a "player" in this scenario.

Three wire O2 sensors use the third wire the "heat them up" quicker on a cold start condition.

MAP sensor is a good call. No "codes" is the most troubling part of this thing!

Symptoms would indicate it happens at a time when the engine needs a "rich" mixture, so fuel pump pressure should be verified.

Ernie