Are you running stock injectors and d-valves?
If not, some of the higher output injectors need a bit of throttle at startup.
With my setup (191's and D3's) I have to give the pedal just a little nudge all the time.
If your stock, I'd check your rubber lines. A hole big enough to cause a problem may not be big enough to see easily and the hoses are tough enough to get to that if you're any bit in doubt, just replace them and eliminate that as a possible souce and then go from there.