2002 Chevy Express Can Mass Air Flow Sensor cause this prob

Vehicle was dying while driving long distances. Would restart after sitting or coasting on 2nd crank. Recently replaced plugs, distributo, and fuel filter. Runs better now that plugs etc have been changed. Starts and runs fine until you have to accelerate much. Slight gas pedal will drive van, but adding pedal past a small window causes the engine to bog down. Vehicle will not climb any hills due to bogginess with a big loss of power, down to just a few miles per hour while on the hills or trying to accelerate normally. Will run ok on flat ground with a feathering of the pedal to avoid the bog down that happens when you push just past the small amt of gas you can apply to get it rolling. Slow progressive acceleration is possible, even finally getting to freeway speeds as long as you don't move past that point where bog down occurs. Can this be related to mass air flow sensor or could this be a fuel pump, or other ideas?