I have a 1989 Mazda B2200 (carb) with around 220k miles and there is air getting into fuel lines. We fixed the problem at first with a new fuel pump but it is doing it again. Any ideas? So far we have changed fuel filter, fuel pump, fixed a few vaccum leaks, replaced the fuel lines at the front of the hard lines.

 

When i used to own carb type vehicles in the past with a see-thru type fuel filter I noticed small air bubbles too from time to time. Dpending where you live the gas may be oxygenated too. I have never noticed a problem with driveability. Are there any problems?