possible oil pressure issues
 

first time post, hope i give enought info. Have a 2005 ford e350 with 6.0. truck is stock with no uprades or add ons. Just shut down, wouldnt restart. Air tested and found STC fitting leaking, but was the new style fitting. R&R Fitting and started, but would not restart warm. Re did air test and found injector seals leaking. While at it, did egr and oil cooler replace, new ICP and IPR. Started without problems. Ran for a few days, now not starting warm, replaced HPOP because thats all that was left. Branch tubes tight and not leaking, no air on last air test, but did notice it takes several turns to get oil pressure on gauge. when running, very stout and no problems, just cant get it started. Catalytic convertor solid, not plugged, what did I miss. any help would be greatly appreciated.

Did not mention, but when injector seals were replaced, also did new dummy plugs and stand tubes. After cycling 3-4 times, does start warm, but getting harder to start. Thought it might be lpop, but pressure good and consistent. Checked regulator behind lpop and full of oil when removed. As this is a van, oil filter mounted at left lower block eith supply tubes to oil cooler, oil filter assy, was leaking, installed new assy, stock from ford. Have not checked fuel pressure, but upper filter bowl does fill up when key on, but would fuel pump cause hard start warm? I cant see what Im missing, but the proof is in the hard start. Anybody have this happen? I cant havr the only 6.0 that does this.