I've got a 97 7.3 5 speed that when I drive it down the road it is slow as all get out I have no power in any gear but first and a little bit into second but other than that its slow just has no power at all. I have replaced the IPR because it didn't want to stay running but now it does and I have injector harnesses for it but I haven't put them on yet. I've changed the fuel filter and changed all the oil in the motor, tranny, and transfer case but I just can't figure out why it doesn't have any power. Any suggestions

 

Try unplugging the MAP sensor. If it runs better then the MAP is bad or the like is plugged

 

A bit more info on the truck, like, how many miles? Is it stock? Was the fuel filter black when you changed it? Have you tryed using the other fuel tank?
Have a compatible scanner that can read live data?