Have 04 ford f350 with 6.0 have changed hpop and stand pipes am now changing the left rail hose to stand pipe.
the actual pressure and desired stays the same when cranking first time when turned off and restart the pressure only goes to about 600 almost half of desired.
when starting first time the start rpm is only 160 the book says it needs to be 185 could this be the problem? When I try to restart the rpm does not show untill it sits a while.
the ficm and pcm where changed, and the pressure test shows no leaks.
Where are the dummy pipes everyone is talking about the book does not show them, I checked at ford and the view on their computer did not show any.

 

Your truck does not have dummy plugs,, the late 04 and up will have them. You said you replaced the flex tube to oil rail, that is how I figured that out. May be the starter starting to go up, when it heats up it might be binding some causing the low rpm, mine is the exact oposite, I have to crank it over to warm the starter up to get it to spin fast enough.