It's interesting about the smaller throttle bore.

Lots of people are quite OK to accept the story about exhaust. Use a smaller exhaust because "you need more back-pressure" which is BS. The car will have more power when there's less back-pressure. But it's not a steady-flow problem, it's more of an acoustics problem. Exhaust pulses reflect around and either help or hurt the next pulse.

The intake thing is kinda similar, think of it as an acoustics problem.

 

Correct. Acoustics and pressure. The pressure should actually not be back pressure. When your exhaust is tuned properly it actually pulls the pulse behind it. Shipo was right about the throttle body, when the hole is to big it wont atomize the fuel properly due to lack of velocity and/or turbulence. The hard part is finding that perfect balance. In my opinion if you want to do it right you should get your intake system where you want it, then figure out the exhaust. But I dont have the loot for that and unfortunately I don't have an R&D team either.

 

Well, there's no fuel injected into the throttlebody, so fuel atomization has nothing to do with it. That would be sizing of the manifold runners and the ports in the head.

There's a couple older Civics with throttlebody injection, but MPFI in the ports has been normal across the Accord line for quite a few years.