RE: STALLING
It actually sounds to me like the vent line is connected to the carb. When the tank is completely full it'll draw fuel from the tank, but after a couple of minutes running the level in the tank falls below the "vent" line.
Have you ever pumped out the remaining fuel in the tank at the end of the day? Can you pump it from the carb line? If the carb line is actually the vent, you won't be able to pump fuel from it.
Dennis-