detroit 12.7 fuel psi

guys i have a 99 12.7 borg warner turbo and tuned by reputable tuner.. im chasing a intermittent low power issue at low rpm and rough engine under power.. i have a fuel psi gauge zipptied to the mirror bracket. i have been monitoring the fuel psi as i drive .. can anyone tell me what the fuel psi should be while under power.. yes i know spec shows idle 20 psi and 65-70 at govern rpm. but what about when the engine us pulling ... if i am 65mph 1400rpm and start up a hill once you get into the throttle the fuel psi drops to 48lbs as the engine slowly builds power and begins to gain rpms. at about 1550rpm the psi will jump to 60-62 and you can feel the torque increase.. if you run the truck like a drag car and operate 1600-1850 the psi stays above 62 up to 72 and pulls really good, i feel like the pump is starving the injectors for fuel at lower rpm. but i can not find any info about fuel psi specs under a load.....any opinions would be great ...

 

i have it tee'd in with the fuel temp sensor directly at the pump

 

engine is a new detroit reman it was complete drop in and go. has about 700 hrs on it. no codes injector cut out tests always pass . when i first installed the ecm and turbo it was very resopnsive all the way down to 1300 rpm almost like a cat engine.. then it slowly started to get sluggish under 1500 rpm more hesitation or lag as you would throttle it .. so i put the fuel psi gauge on and a site glass on the return ,no air ..coming out of the head ..stills runs ok but has a dead spot under 1500 and the dead spot seems to fall in line with the fuel psi being under 60 lb. as the rpm slowly build so does the fuel psi and when it hits about 60 psi it comes alive .again... just made me wonder if it was a psi issue... it also seems to have less psi drop when the tanks are full of fuel.. we have a snapon scan tool so i can perform a few tests but its kinda generic

 

This truck only has the Davco. This morning. Fuel tanks are full. Fuel psi NEVER drops bellow 58PSI. And the amount of power below 1500 rpm is is considerably higher. Seat of the pants. ‍♂️‍♂️