Right Turn Low Fuel Stutter Stall

When my tank is slightly lower than 1/2 tank. It will stutter on steep up hills or right hand turns. Stall if I floor it. It has an almost new Fuel pump & new Pickup screen on it. Please help. Could it be that the tank is not sealed from outside air?:eek7:

What year is your Mustang? If it's a newer one with OBD-II you will have the MIL illuminated with a code stored for EVAP failure if the gas tank isn't sealed properly.

Thanks for the quick reply. It is a 94 mustang. I know that the tank spout is noot sealed as last time when I installed the new pickup that it was never tight where it enters the tank. Would that cause iit if air can get in the tank. How could I seal it iif so. I notice on my other car that when you open the tank to put fuel in it hisses like its compressed or something the mustang doesn't obviously because air gets in through the inlet pipe as mentioned above. The metal harness which holds the fuel pump in also appears to hold a larger fuel pump than the one installed. It is a correct aftermarket model nfor the car though I checked. Could someone have installed larger or performance fuel injectors and needed a larger fuel pump for it. If so would that cause the problem. Or would that happen at all times and not only right turns. Thanks again for any help

If they have bigger injectors and the tune and MAF to go along with it, than the fuel starvation would be a problem any time you hit the throttle past what the fuel pump can provide. And air getting in the tank would not cause it to stall out, but would be an EVAP system failure if checked.

When was the last time you changed the fuel filter?