You are not providing enough information.

Are there bubbles in the feed line?
Have you tried richening up the high-speed needle (try 2 - 2 1/2 turns open from fully closed)?
Did you mess with the low speed needle? -- Try turning it 1/2 turn counter clockwise?
Is your pressure line plugged?
Have you tried changing fuel lines (including tubing inside the tank)?
Is it an inverted mount?

We need more to go on -- describe the set-up in some detail, as well as all of the remedies that you have tried.