My 98.5 had a new injection pump put on by a dealer, along with a new ECM at around 125,000 miles. The truck now has 157,000 miles. One time, I was hauling a load, with the VA off, in 4th gear, 1300 rpm, and the truck kind of "coughed" - it lost power for just a second, then came right back. Then, last night, I was pulling about 10000 lbs, (VA was on) and if I floor it on a hill, about 2100 rpm, 12 psi fuel pressure, 1200 egt, and 28 lbs boost, it is like I shut the truck off for just a second, then I let off the pedal, and it comes right back. It just loses all power, and then comes back. It did that on 3 different hills, and it only seems to do it if I floor it. Other than that, it has good power, runs beautiful, and starts good. I haven't taken it to the dealer to check for codes yet. I am going to change the fuel filter, but it shouldn't need it yet, my air filter is clean, and I have no boost leaks. Any ideas?
The 12 psi is at the injection pump too, not at the filter. Thank you

 

sounds like the dead pedal to me. take it to a parts store and have the codes read. some vp's run 5 min. and some run 200k. could be a apps. we need the codes before we can help much

 

Had this same problem with my banks system. They (Banks) said the fix was to ground the otto-mind at the ecm ground down on the engine block.... Hope this helps