260E sooty plugs

[gtrpicker]

1987 260e
After a trip up the road and back (about 8 miles) the idle stalls and it will not restart until I pull the plugs and clean them.
so far:
Fuel filter
new ignition coil
Changed the EZL
changed the fuel distributor
changed the EHA
changed the idle control motor
new cap and rotor
new air filter
It doesn't matter what make of plugs they all soot up.
The duty cycle reads 17.2 - 18.1 and fluctuates. If I lean out the mixture to get a better duty cycle reading then it won't start.
With all those parts changed it has done nothing to help my problem. The ovp appears to be functioning. no ABS light on. If I unplug the eha the car will stall.
I've search the previous posts, thats why I changed all that I did.
What have I missed guys??