I'm working on a 91 international 4700 box truck, starts and idles just fine but under driving load loses power and dies. Will start up after about 10 min. changed out fuel filter/ with no improvement. Any ideas??

Is that a diesel?

Yes, in line 6, 5.9 / 360cid

Sometimes, fuel pump clearances increase, when it warms up under load, and fuel pressure drops. Check the fuel pressure, after it dies--it may need a new fuel pump.