Good question Jody -- I have no clue!
My throttle bodies are 2"... and based on the IDA Weber "platform"....
I don't know what the flow rate is - if you stacked all 8 and did a WOT -- but I'm thinking it's way more air than my motor will ever need!!
In fact - I've thought about that many times - thinking about the blades on a 850 CFM Holley -- and then comparing that to the "area" of 8 x 2" holes... I'm thinking these manifolds have to be capable of 1200 CFM plus?