You have to watch that you have adequate atmospheric pressure (venting) on your fuel tank/cell whenever you increase the volume of the pump, the inlet side of the pump should really (ideally) be gravity fed (it really shouldn't "suck"), 2 thinks would cause a pressure differential the first is a restriction the secongd is a lack of atmoshpheric pressure on the fuel in the tank.

Increasing the flow rate can amplify a problem you didn't know you had until you made the swap.

Don't forget G-forces have an effect on your effective flow rate, G forces effectively multiply the mass of the fuel in terms of GPM or Pounds/hr that's why harder launching cars have much bigger pumps than would need to run on a Dyno.

Check the obvious things first....don't throw the baby out with the bathwater.