The only thing that can make the engine rev up is more air, so I still thing you need to take a look at the idle air system. I've seen big steel ball bearings stuck in the blowby hose to cut the idle back!
Places to look:
Seals between the intake manifold halves (there are 8). Spray some carb cleaner down there, if the idle speed changes, take the manifold off and re-seal it.
Seals at injectors.
Y-shaped idle air hose from idle valve to manifold. A crack here can give you fits.
Is the mechanical advance working properly, and is the timing set correctly? A broken spring on the mechanical advance can make the idle surge. So will a bad vac retard diaphram or hose.
Fuel pressure fluctations from a bad damper or pressure regulator. A bad pump or relay will cause the car to quit, I think.
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!