The air sensor pot's resistance rising sharply is not a good sign. Infact, the jumps should be less than 2K if you are moving the plate really slowly. Did you get a larger jump than that ? And was the jump close to the zero position, because that could explain your hesitation around 2K rpm.

And you dont have a catalytic converter, but still there should be enrichment current on the EHA. Do you get 10-20 or so ma when you just turn the ignition switch to run, before starting ? Let me check the expected test results on EHA for your car again.

__________________
Saumil S. Patel