I have a 2005 F450 6.0.I January it just quit and would not start. Had it towed to a mechanic. He changed the IRP sensors, and it was fine ran great until 2 weeks ago. Once again towed it to the garage. We tried a new sensor but computer said we were only getting 145 psi out of the HPOP. Mechanic said well Ford had problems with that pump. Said fine put in a new one. Also had the oil cooler changed and Did a EGR Delete while he had it a part. All back to gather cranked it, Still only 145 psi from the HPOP. Checked the low pressure pump and its fine. So onward we go. We replaced the D plugs in the HPOP rail for the injectors and new improved stand pipes from Ford. Again cranked it and still only 145 PSI out of the HPOP. Anybody got any ideas. Redone the HPOP system from end to end and still have this problem. Mechanic is now suggesting Injectors. I don't want to guess at 1700.00 dollars worth of injectors.