simple paint question

im spraying regular run-of-the-mill lacquer primer on my truck and i have a few questions concerning the paint gun... i am using an HVLP style of gun and it currently has a 1/4 tip in it. I have noticed that the paint applies fairly dry and it has a very rough texture to it that is somewhat odd. what could cause this?

1) might i need a bigger tip?
2) maybe more thinner?
3)less air pressure at the gun?
4)moisture in air supply?