FUEL PUMP ISSUE ?

MY 94 CHEVY RUNS GREAT IN ALL CONDITIONS EXEPT WHEN I AM PULLING A LONG HILL. USUALLY ABOUT HALF WAY UP THE HILL ON THE INTERSTATE (RUNNING BETWEEN 55 - 70 MPH) THE ENGINE WILL SORT OF MISS, KINDA OF A SPITTING SPUTERING SOUND. I CAN FEEL THE TRUCK SLIGHTLY JERKING.
HERE IS THE INTERESTING PART. ALL I HAVE TO DO TO MAKE IT STOP IS TO ACCELERATE. EVEN THE SLIGHTEST AMOUNT OF ACCELERATION AND THE TRUCK SMOOTHS OUT. ITS FINE WHEN I'M ON FLAT LAND, BUT IF I'M PULLING A HILL AT A CONSTANT SPEED, I'LL GET THE JERKING.
NEW TRANSMITION A YEAR AGO DIDN'T HAVE ANY AFFECT ON PROBLEM.TRUCK HAS 176,000 MILES ON IT.
THE ONLY THING I WONDER ABOUT IS, ABOUT 3 YEARS AGO I RAN OUT OF GAS AND HAD TO HAVE A NEW FUEL PUMP INSTALLED. I'M NOT SURE IF THE PUMP WAS OEM OR NOT.
ANY IDEAS ?    THANKS, BILL