You say you pressure tested the fuel lines. How exactly did you do the test?
Did you take the lines out of the tank?
If you did not and you just pinched off one line and blew air into the other line to pressurize it, while both lines were still in the tank, you have accomplished nothing except check the tank itself for a leak. If this what you did then you may very well still have a split in the pickup line and are sucking air from inside the tank. Take the lines out of the tank to check them.