That's what happens when you throw parts at it without determining the cause of a problem.

You have a bad OVP -- if it gets hot, the solder joints are bad and causing excess resistance.

Replace the O2 sensor unless you can verify that it is working, they don't last forever and appearance means nothing, it has to be electrically verified.

Your hesitation was most likely bad idle control valve hoses (rock hard, eh?) causing a vac leak. Idle valve can be cleaned with carb cleaner spray, it shouldn't have residue in it.

A bad fuel pump relay will cause intermittant stalls, rough idle, and mixture control problems from inadequate fuel delivery. So can bad fuel pumps.

You now need to properly set idle mixture, it's probably way off -- when the computer attempts to control the mixture it goes overlean and causes low vac, rough running, etc. This is probably more vac leaks, there are a number of sources.

These can be expensive to restore..... Much more expensive it you start replacing things to see if they are bad!

Peter

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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!