No modifications, truck is stock. 45K, transfer pump and vp44 replaced due to getting frequent 0216 codes. From delivery to that time I followed the owners manual and used just good quality diesel fuel with no additives. First lift pump held 14 psi at idle and 12 at cruise and 10 at wot, it was a good lift pump, but was replaced by dc as part of the vp44 replacement ritual.
With vp #2 i have used standyne lubricity additive from day one. Second transfer pump held 14 psi with engine off, 10 at idle and 6-8 at cruise. On a recent long trip I was cresting a hill, unloaded, and watched the fuel pressure dip to about 4 lbs and the check engine light came on at that time. Several hours prior to the pump failing to maintain pressure the gage would take a major dip down to 2 or 3 lbs when I engaged the speed control and the truck was attaining cruise speed.
My truck is a 2002, HO CTD which i bought new.