Truck doesnt start sometimes, I can get it to start if I "prime" it (turn the key to on 3 times and the forth time to start) and it will start. Once it is started it runs rough almost like I am loosing vacuum pressure. I have been getting O2 sensor codes and changed out the O2 sensors, didnt matter. Here is what I have done:
new O2 sensors
new plugs
new wires
new fuel filter
checked fuel pressure (60+psi)

Only thing I can think of now is blocked catalytic converters. Please tell me there is something else!!!!!!!!:banghead:

What does the fuel pressure do when you turn off the ignition? If it does not hold pressure, then it is most likely fuel pressure regulator or stuck poppet.

Do a search on "fuel pressure regulator" and you will see if is fairly common and results in hard starting especially when it sits for 30 minutes to an hour or more.

//2000CAYukon