7.3 sputters at 45mph and dies

[purdueagford]

got a 2002 7.3L that is starting to give me fits. The truck will start up fine in the morning, or after sitting for a while and idle like it's supposed to. As soon as I take off down the road and get to around 40 mph, the truck loses power and acts like it's not getting fuel. i have to pull over and stop and keep the truck running with the skinny pedal until it will idle ok again. After that it is fine until it sits for a long time again (overnight).

i'm pretty new to diesels but i read on here to check the fuel filter. so i replaced the fuel filter because it was pretty dirty. the water light is not on and clean fuel came out of the drain. problem is still there. any ideas?