It certainly sounds like your persistence and exorcism has been successful. I need to find the formula to exorcise mine!!!
My question to you is: has your gas mileage been affected by all these events? My headache is not too different from yours, but my mileage is down about 25%.
Mine is a 93 300E 2.8. A slightly different engine. Just before 95k mi. the CE light came on -- O2 sensor bad. I replaced it with a Bosch generic unit (after calling Bosch to make sure it was the right one -- 4 wire interface). In a couple of thousand mi., the CE light came back and would not go off. This time, to a dealer, who said the wiring harness was shot. The dealer replaced it at no cost. Since that day, the gas mileage has gone from about 25 mpg to 20. That has really has bothered me.
A few days later, the CE light came on again. The dealer said its the O2 sensor -- running too rich. This time, I had it replaced with an OEM O2 sensor. A little while later, another CE light -- this time, the EGR code. Got it fixed. Next time, the intake manifold length tuning flap. Got it replaced. None of these has brought the mileage back up. Now, it's giving the 26 code. After reading your thread, I'll check the vacuum on the tranny delay shift switch (and the switch). That should remove the 26 code, but won't account for the gas mileage drop.
Any ideas on what might cause the reduction in gas mileage on this car that runs perfectly -- now with 134k miles?