2250 Dreaded Fuel PUMP

[Smooth]

Pulling what little hair I have out... Catch up - Replaced to the updated Fuel Pump and converted Fuel Lines etc. But when test drove and would accelerate truck would die out and lose power and throw Fuel Rail Pressure code.. Afterwards it still badly failed the Fuel Pressure Leakage Test losing 10K psi in 1 Min.... So

Replaced the Fuel Relief Chk Valve.
Ran the Fuel Leakage Test and it passed hardly losing any PSI at all
Proceeded to run Leakage Test the 2nd time and 45 sec in Insite stopped the Test stating High Fuel Pressure Detected

Truck idles Great , I can hold the accelerator at Diff RPM and runs fine. When i get to 1600-1700 range truck will flutter and fall on its face.

Digging into trouble shooting but wanted to throw this out there in case anyone had experienced anything similar or had an idea....