2 inch pipe vs 2 1/4 inch pipe

All this is nonsense. This would have SOME merit IF you had a straight through system, no mufflers.

But airflow is STILL affected by

the bends in the pipe, IE the number of bends, the angles, and how restrictive they are

the length of the overall system

You stick a pair of mufflers in there and the whole theory goes right out the window. I'd bet money that 2" is too small on any good running 360, and 3" is not too big

And what are you gonna do "if you discover" that to be effective at scavaging, your system needs to be longer or shorter? You gonna stick the tailpipes out 2' behind? You gonna cut them off underneath and gas yourself?

The lesson here is "always run open headers." The fuel mileage you gain will EASILY pay all the noise tickets you get "NOT"

Stroker's right. We could all donate a LOT of money to research on this, and every time somebody changed mufflers, you'd have to "retune" your exhaust for that last bit.