I also had a similar problem. I replaced the entire fuel line, but that didn't help. I then bypassed the fuel/water seperator and it worked great. For about $60, I replaced the fuel/water seperator and the engine is running air free.
As the previous post mentions, I believe there was something in the seperator blocking the fuel, which in turn made the engine start sucking air.
I would also check to make sure the screw used to bleed the engine has the brass gasket on it. If not, that could also be an air source.
Good luck
