Why can it be too big?
Deep Roots explains it well:
Annular booster carburetor flow test
By being more of a restriction the Same volume of air has to move faster around and through it. The engine pulls more fuel.
Main air bleed, jetting, and pvcr’s need to be changed to accommodate that.
Evaluate the well designed Autolite carburetors that came with annular boosters. Pump shot is small, idle circuit pretty much just addresses idle, transition is almost non-existent as the booster starts early and does almost all of the metering. The rest is addressed with bleed air.
