I had a problem with the auxiliary air regulator on my '84.    This is
situated beneath the bellows intake.       It has a heating element and a
bi-metal strip in it and mine went to ground sometimes, depriving the
injectors of power as they are normally grounded through the ECU, and the
engine died.
Of course when the valve cooled down, the short went away and injectors were
once again grounded by the ECU and the engine ran.
This valve is connected to the injector wires inside the harness
Try disconnecting this valve.    If the problem goes away its your culprit.
If not, its something else in the process of elimination .
Good luck,     Steve