Check the ground wires on the side of the intake manifold. They can corrode and break at the ring crimp. Pull the connector off the ecu temp sensor while its running. If it starts running worse (really rich) then the sensor and related wiring most likely aren't the issue.

I'm happy to see it go to a good home. I'll let you know if I end up finding anymore 4000 parts when the shipping containers get unpacked.

Thats one nice looking 4000 you got there. I wish mine looked that good. Im strongly considering parting mine out. PM me if your interested in the AAN and vems.