Same thing happened to me. Go pedal to the floor and barely enough power to crest a hill. Mine ended up being a worn out injector pump. I advanced the timing a dime width and it lasted just long enough to have the remanufactured ip delivered. After the replacement and retiming she was back to normal. One of the things I noticed before it crapped the bed was white smoke while coasting, especially down hill and I mean like a mosquito foger! Mine is a 94 with factory turbo and e4od. Had about 320,000 miles on the factory ip, which was about 220,000 miles over due for replacement. Don’t freak out man, there are lots of good folks here with knowledge to share willing to help. The more details you can provide the better though. I think your new injectors are requiring more pressure to pop than your old ip is used to with the old equally worn injectors. What’s the mileage on your ip? If it has the original grey paint from Navistar then it’s probably way over due.