I’m going on a separate track of thought. It seems the stalling occurs when your foot is on the brake. I’ve seen this before, and it was a brake booster that leaked when the pedal was pressed, causing a large vacuum leak at idle that causes the engine to stumble and stall. This can be replicated in the driveway by simply pressing the brake and seeing if the engine stumbles. In both casrs I’ve seen, you can also hear the leak under the dash.