97 Pete 3406E starving for fuel pulling hills

I have a 97 Pete with a 3406E cat. About a month ago my truck started to act like it needed more fuel when climbing hills. The issues started small only doing it once in a while. I had the fuel filters changed along with the old rayco filter changed and replaced with a regular filter. I've replaced all the fuel lines and splitter valve and still does it. I took a day off and cleaned all the electrical plugs thinking it might be that. The next day it ran fine for the most part and didn't act up as bad. The following day the truck was horrible. The truck runs fine empty and loaded until I get about 8th gear and the rpm tach jumps around and truck just acts like it doesn't have enough fuel. I've just put a new hand pump on for the filter thinking it might be that. I'm going to test it tomorrow but if it's still acting up could it be the transfer pump?

I'm going crazy chasing this problem

 

After a month of trying to figure out what's going on and no codes popping up finally my check engine light came on today pulling a hill. It showed code 32 which is a throttle positioning sensor. . Never thought I'd be so happy to see a check engine light but I was. Going to put a new sensor in the foot pedal and fingers crossed it fixes it. Thanks for the response

 

I have a TPS ordered and will install it tomorrow. This morning the truck ran like it had no issues until about 3 hours into the trip. What's interesting is now the check engine light is coming on one I let off the throttle and the jack engaged. It has to be in the throttle. If this doesn't work I'm going to do a cut out test on the injections. The truck only has 280k on a complete rebuild. It's a 97 , with 880k original miles. My first thought was it sat for a long time an could of been junk built up but I've replaced all the lines. I put injector cleaner in it yesterday not expecting it to cure it just maybe help it.

 

I'm going to go over all the wires again this weekend. I cleaned every wire I could find last week and it ran fine except a couple times. I did spray the foot pedal but never took it apart.