If the car starts and idles, I doubt you have much of a vacuum leak. if it idles poorly also that would be a possibility. If too much air is a hypothesis, then add fuel. The simple trick is to lightly push down on the airflap (air filter housing removed). If the engine runs better, continue till it starts running worse. If the speed when it runs the best is above 1000rpms you definitely have too much air entering. It could still be metered air though if the idle valve is too open.

Adjust the fuel mixture then at the adjustment till best running. Now try to accelerate. If it still dies, do the gentle push thingy again while accelerating by hand with your other hand. KEEP YOUR FACE away from the airflap as it could backfire. Be sure your frequency valve is buzzing during all of this.

If you can not overcome this hesitation with a functioning frequency valve and added fuel then one might look to low secondary ignition voltage or a shorted path to ground. Rotor fingers are common shorts to ground. It happens when the short becomes conductive at a voltage just above what is needed to idle; say at 11kv. At 8kv the car idles but as the loadingf increases off idle the requirements grow to say 14kv. If the rotor shorts at 11kv then all the spark passes to ground through the distributer shaft and teh engine dies.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician