For what its worth, I disconnected the O2 sensor & tested the vehicle connector. At the pin in the square plastic side, it measured -.04mA with key off, and resistance of 11.2 ohms--I did the same resistance test on the 91 300e with the good sensor ( 70% duty cycle with key on, engine off), & got .74k ohms, obviously a different reading. Does this help identify the problem?

I have never tested at the EHA, so if you would be kind enough to explain where to place the probes & what setting I use on the DMM, I can do it. Also, which black box behind the battery is the computer? Is the ground near the negative on the battery? If the computer is bad, I could swap it for a good one from a 91 300e recently totaled (same for EHA, if that is advisable). Thanks for your continued help-the good news is that the 300ce I adjusted with your help runs just super.

BTW, on this same 87 300e I unplugged the instru cluster to swap the outside temp LCD & while pulling it out I seem to have disconnected a vacuum hose ( I hear the telltale hiss, which wasn't there before) , & I can't see or figure out where it goes. Do you know? Thanks