2013 EB Long Extended Start - Key off fuel pressure

Started having an issue with long or extended crank for the truck to start on cold start ups. Starter engages, turns engine over at the expected rate, engine struggles to ignite for about a second and a half longer than normal, then fires off. Tried easy potential fixes, plugs, coils, battery. After an initial start, subsequent startups happen no issue if the truck sits for two to six hours. If the truck sits longer without a start you the symptom is noticeable.

Trying to determine what's normal behavior on truck fuel pressure at key on and key off. I'm seeing the high pressure side bleeds off the longer the truck sits since last start. Not sure if this is normal, circumstantial, or part of the symptom. Anyone know the correct behavior of the high pressure side fuel pressure after key off? Should it maintain pressure?

I've observed the HPFP high pressure side appears to lose rail pressure the longer it sits. Idle seems to be in the 800--900 range. After four hour of shutdown it was 788 psi, after six captured 356 psi, after 14 hours it was 55 psi. Not sure if this is normal behavior or part of the contributing symptom.

Anyone know of the expected good behavior from the high pressure side after key off?