IFSM Leaking

[berrytrucking94]

currently around 508k miles now, the sputtering/skipping is so bad it can barely make it down the road. cold weather makes it worse. it won't run decent until the fuel is mostly up to temperature, usually ~hour into operating. truck is parked until i can figure this out.

ecm rail pressure reads normal, there was a low fuel pressure code in there though (0482)

gear pump still forms some fuel residue around it

any recommendations on checking air in fuel lines w/ a tube or sight glass? never done that procedure before

could bad check and relief valves cause sputtering?

any help is appreciated! no shop knows these motors around here and frankly i do not trust them