Engine/Transmission (1998.5 - 2002) What could cause this?

[RConner]

Occasionially the truck bucks if you start it too quick and put it in to gear to fast. Today it did it a couple of times and then I realized my fuel psi went down to 11 at idle and 6 to 7 while cruizing. When I got home I turned it off let it sit and started it back up and the fuel pressure was back to normal 16 to 17 psi at idle. I have not went back out and driven it. I will later. No check engine light is on. Does this sound like the lift pump is going. This is number two and I am also on number two vp44. The fuel filter was just change a month ago. I also have the vulcan big line kit on my truck...