It is in the gas tank, but it sits in a small internal tank specifically so the fuel will not run away from the pickup screen during turns. The clue to something being wrong inside the tank is the stalling will not occur until the fuel level drops to less than about 1/4 tank. If the stalling occurs when the tank is full, there is no way that much gas can rush to the side of the tank and let the pump suck up air.
A much better suspect is a wire is rubbed through or a connector is making intermittent connection, and the circuit is broken when the engine rocks or shifts. If you still suspect the fuel system, connect a fuel pressure gauge, run the hose under the back of the hood, and clip it to the right wiper arm so you can watch what happens when the problem occurs. Many auto parts stores rent or borrow tools. They will have a pressure gauge.
Dec 21, 2016 at 12:19 PM
