I think each TB has the ability to flow up to 1000CFM. However, that is not very realistic. With port EFI any changes you make upstream of the injectors is just additional runner, plenum volume or a reduction in restriction. My new intake has three two barrel throttle bodies that could flow as much as 1600CFM with a given difference in pressure, but that is really a limit, not what it will flow. If you assume 100% Volumetric Efficiency, my 446ci engine at 7000rpm would flow 903CFM. I'm guessing I will not use 1600CFM... ever. My little ~840CFM Barry Grant actually worked really well on this engine. But, the combination of runner size, length, and plenum volume of my new intake will increase my VE within a certain RPM range. The beauty of port EFI is that you can not "over carburate" the engine by running a 2x4 or 3x2 set up. As long as you keep the injector sizing close you should be good.