Yellow Rose. All true. Definately should be checked out.
But also if pressure in the feed line for any reason goes up, at some point it will exceed the force of the float holding the needle closed. This problem is worse with larger inlet valves as they have a larger area. Force = Pressure x Area
If it turns out that its not carb's system, then its worth doing whatever it takes to see if its the pump and regulator. I hate to suggest buying anything new when possibly not needed, but one way to test it out is swapping in a pump with internal regulation at 6psi or less and eliminating the regulator. A stock type pump would be fine for just seeing what's going on. Maybe borrow a used one or parts store.
