Tell me this, does the harness plug for your EHA still have its plastic housing and / or has it been recently replaced?

Sounds like one I fixed where somebody had inadvertantly switched the wires on the EHA b/c the plastic "pin bushing housing" was missing. This caused the EHA to pull fuel out when revved instead of adding fuel. Lambda works in reverse and the problem compounds on itself. Assuming you have good parts that could explain it's behavior.

Try switching the wires on the EHA and see what happens.