I assume that you are talking about seeing a lot of bubbles in the pre-filter at idle.
Do you have any fuel leaking when you use the hand priming pump? Is the pump the old style that is white and unscrew to pump? If so, then the hand priming pump may be causing air to get in the line and should be replaced with the new style primer.
Also, a clogged fuel screen at the tank has been mentioned as causing air bubbles. And depending on the model, a clogged fuel tank vent may cause this.
(BTW, you need to go to "User CP" at the top and edit your signature to include the model # of your car so we know what we are dealing with.)
