A properly designed intake creates a pressure wave that acts like a mini-turbo at a specific RPM, similar to a header creating lower pressure at the exhaust ports at a specific RPM, so both are Scavenged power, free power using the physics of air flow.
Ford(and a few others) tried variable intake runner lengths in the first 2.3l Duratec, IMRC(intake manifold runner control) changed intake lengths to get the "mini-boost" at different RPMs, it does work, just not reliable in real world use, lol, which alot of "on paper" ideas have a problem with
Tri-power(3 carbs) could get better air flow but intakes could also benefit from shorter runner lengths for the cylinders at the 4 corners of the V6 or V8 engine.
Easier to create the reflected higher pressure at the intake port at similar RPM as headers low pressure
Remember, engine power has nothing to do with gasoline flow, 0, nada, with more gas you just get a flooded engine
Air flow is the key, make air flow better and you get more power
Applies to carb or EFI equally
EFI intake design was a little easier because you don't need runners to reach a center hole for carburetor.
There is an upper limit to air flow
When you lose intake vacuum in a running engine then no new air/fuel mix can be pulled in to the cylinders, this can happen at WOT(wide open throttle) if throttle opening is too big for the engine size
If you take vehicle out to deserted road, hook up vacuum gauge so you can see it, then take vehicle up to top speed and WOT, you should still have 1"-1.5" of vacuum, until valves "float"(max RPM for engine/valve springs)
If vacuum drops to 0" before valves "float" then throttle opening is to big
This is the reason too large an intake opening makes engines hard to start, you need minimum of 2" of vacuum in the intake when cranking an engine, to pull in a good air/fuel mix
Applies to carb or EFI
So "slapping on" a bigger carb or throttle body doesn't mean more power, you could lose power