Random HEI shut off

Is the vac adv hooked up? If yes, I suspect a broken pick up wire. When the VA operates, it moves the p/up coil which flexes the wires. After enough miles, the wires will break from continuous flexing. Since this only happens just above idle, & is consistent, it rules out most other things.

You can measure the p/up coil, should be 200-1200 ohms. Flex the wires will doing it to see if it goes open cct.