Sorry for the delay in replying. Have you figured this out yet?
Be sure the idle speed is correct. Your transmission is very simple and relatively reliable, but that translates into a harsh, uncushioned engagement compared to other brands of cars. That harsh engagement can stall an engine that is running too slow.
Good observation about the vacuum lines. Also look at wiring hanesses. In particular, try removing the air cleaner while the engine is running. The connector on the Lean Burn computer could be loose and making a poor connection when the engine shifts position. Wiggle the distributor connector too.