1988 Ford E-Series Van shuts down while driving

i start it and it runs fine. after im going down the road and it warms up it cuts out almost as if it runs out of fuel. if i take my foot off the gas and let it catch up then hit the gas again its fine for a bit then it will do it again a couple of miles down the road. i had to put a new fuel pump relay in last week because the old one get water in it so it shorted out and drained my battery. i also put in a new fuel filter, octane booster, and stp ethanol treatment today