Make a harness so that you can monitor the duty cycle, and better yet (if possible) the EHA current while driving. This will allow you to see what is happening.
If you set the mixture with the O2 sensor cold, it may not be on the correct mixture while driving. You should be getting a little enrichment on acceleration (lower duty cycle, I think), going back to 50%.
EHA current should be near zero at idle, go positive on acceleration, then go to -20 or so on closed throttle deceleration (shuts off the fuel). If you have no change on acceleration, you aren't getting acceleration enrichement.
That is usually the result of a bad potentiometer -- it "tells" the computer you are moving the throttle and airflow is going up.
You should also check the base position of the flap in the mass air flow sensor -- must be at the base of the cylindrical section at idle -- and your base fuel mixture. You can unplug the EHA and see where the duty cycle goes -- without the EAH plugged in, there will be no feedback, so the O2 sensor just sees the current mixture, doesn't change it. If the duty cycle changes off scale with the EHA unplugged, try to set it to 50% and see how it drives.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!