Fuel pressure leakdown is most likely the pressure regulator, but the accumulator could be bad as well.

If it smells of rotten eggs when it runs smoothly, I would suspect vac leaks at the manifold half connections and/or injector seals and possibly the idle control valve. Another possibility is the plastic boot between the throttle body and manifold.

Set the idle mixture to spec and then look at the spark plugs -- if they are different colors, you have a leak OR a dripping injector -- dribbly injectors will drive you nuts getting idle mix correct, but will usually work just fine off idle. If one leaks, the mixture will be too lean for the other cylinders when the CO is correct.

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!