We did it
Chuck, the blue wire was the hot one. I cut off about 1/4-inch of the insulation to get a good, clean contact, I confirmed the O2 sensor with a 69.3% reading & was able to adjust the warm engine readings of apprx 65% to appx 50% with a very small turn of the screw. The car purred, with no shakes or missing feeling. And it was quick and smooth from a dead stop, I couldn't believe it was a 1988 300CE!! When done I separated all the wires from the blue one by putting them into a short piece of plastic tubing & then wrapped them all, including the blue, in electrical tape to keep them clean & away from everything else.
Thanks to both Chuck & Peter for your time & sharing so generously of your knowledge. The people like you who reply on this board make it such an unbelievable resource.
Now, on to the next problem...the neutral safety switch on the 87 300e ( to be posted soon)