Some smoke isn't unusual when pulling a grade - daBenz will smoke hard before it quits pulling, then keeps smoking in third until the fuel is burned out.

The vacuum operated governor takes a little bit of thinking. The idea behind the mixture controller (the venturi upstream of the intake manifold) is to pull vacuum in the venturi at fast engine speeds, which pulls the diaphragm (the inside end of the vacuum box on the injector pump) against the spring in the vacuum box. The diaphragm is connected to the injector pump rack via a linkage that you can shim on the diaphragm side of the linkage, but you have to pull the vacuum box. And I hate pulling things apart that aren't broken.

Try this first: chase the vacuum line back to the mixture controller and pull it there. The line should hold vacuum. If not then either the line or the vacuum box is leaking. If the box then probably the diaphragm. If the line does hold vacuum then pull the air hose upstream of the mixture controller and look at the vacuum valve. This can get crudded up, especially if an oil bath air cleaner engine is run too fast or if the valve hasn't been looked at in a while.

I make sure the valve in the venturi is working, make sure the line and vacuum box are not leaking, and leave it at that. Then I make sure the butterfly valve in the venturi opens all the way when I roll the foot throttle linkage to the full throttle stop, and leave it at that. I can pull anything in third gear - a little smoke on the 7% grades at 45 mph. Last long road trip was 3600 mi to Seattle and back on two lanes and averaged 36 mpg with the 4sp manual, so I'm satisfied. But I'm also a bit fanatic about clean fuel, and that seems to keep the whole engine system working. Leaky injectors will smoke something - either out the tailpipe or wreck the glow plugs.

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daBenz - 1970 220D