Runs poor after leaving Fuel on

[Harpkatt]

I'm a little confused, occasionally when I mistakenly leave the fuelcock in the on position when running into a store or similar short trip my 30 RPU won't run properly- Bucking and hesitating. I can get the truck to idle find and start without issue but any throttle and the engine tries to die. This never happens when I shut the fuel off. No amount of driving clears it up either. I'll turn the valve off to lessen the fuel in the bowl but there's no change. Anyone ever experience anything similar?