Originally Posted by professor

Put an Ammeter at the EHA (in series) and measure the current. You should oscillate around 0 Amps -1mA to +2mA. That should tell you that the EHA is working at regulating the pressure differential inside the fuel distributor based on the feedback.
Check your fuel pressure readings:
Main pressure, that is before the distributor (the cold start outlet is a good place).
Lower pressure, that can be done via the test outlet on the distributor.
You should get a specific difference between the two, check your manual for the value.
If that is off and you tried the EHA to get it then you have a problem with a CIS component. You will have to trace that throughout the fuel lines.
In your case, it's possible that the computer can't keep up and from the looks on that signal you may have set it where it went rich. You could see it drift then it's like the computer decided not to play no more

Please note that EHA and Lambda adjustments must be done a hair at a time. NEVER full turn!