same thing happened to me last week, i have the bd pusher pump that mounts on the frame, and it just failed. the night it failed it ran real rough and did the same thing, bogged terribly and even blew some white smoke. thought i blew a head gasket, but it was the lift pump. my vp is fine thank god. do you have a reading on your fuel pressure? if not take the fuel filter out, bump the motor (just barely hit the starter but not enough to let it turn and fire) this should get your lift pump to pump fuel if you arent spraying fuel then i would say its just your lift pump.