Could be a small split in the "accordian" hose from the amm to the throttle body or one of the hoses to the idle speed motor.
Take it off and flex it in front of a bright light.
That may be why it doesn't idle with amm disconnected. Overall performance could be the amm though. Check the spark plugs, wires, and cap+rotor.
Pull the small hose to the pressure regulator, it is mounted to the intake manifold and is approximately just behind the distributor cap and PS. See if that changes the idle or if it leaks gas.
I have amm on order for my 83 244dl. I have intermittent stalling and lean conditions during acceleration, pinging and knocking, at times. I have been through just about everything also. My amm is about 12 years old, a rebuilt that came with the intermittent pinging.
Larry