You need to have the fuel distributor flow tested to make sure you have proper fuel delivery to all cylinder.
Do check the mixture, too -- if the fuel pressure was low due to dirty filters and a weak pump, and the mixture was set under those conditions, it will now be off from higher pressure and better flow. The EHA can go bad, too, resulting in a small fuel leak and unstable idle.
Also, I would check the condition of the idle control valve hoses -- when they get old, they leak and cause all sorts of mixture problems. You will only chase your tail until you have any vac leaks fixed.
Check the spark plug wires, too -- if they are old, they will fail and you get no spark to some cylinders. Expensive, but the car won't run properly with bad spark plug wires.
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!