throttle problems any ideas?
 

I have an 01 cummins stock expect 4inch exhaust and intake and just had the lift pump and injector pump replaced. I have been to a few shops and nobody can figure this out, now at around 2000rpms about 70 on the freeway cruising on flat ground everything is fine than I try to give it a little throttle to speed up I lose power, I can back off the throttle and have power back or go more than half throttle and have power so it feels like a dead spot.. if that makes sense. the only time I can really notice it is on the freeway and the volts on the tps seem to be normal. hopefully I explained it good enough!

any help I would really appreciate it thanks!

throttle boost specifications
 

How much boost is your truck showing while this symptom occurs?

FYI -- The wide open throttle boost specifications: standard engine, 22-24 psi;
HO engine 25-26 psi.

just before the symptom im at 6-8psi than drops to 3 or less when I hit the dead spot

and wide open I can only hit 17-18psi