Induction system volume

Here's something to think about: How much of an effect does the volume of the induction system really make? If you've got…
2.5" intercooler plumbing x 6' = 4.9in2 x 72in = 353 in3
3.5"x10"x16" intercooler core = 560in3 (10% charge air portion) + 2x3.5"x10" end tanks = 126in3
4L of intake plenum = 244 in3

Totals 723in3 = 0.418ft3

Now, if you're getting from 0-60 in under 4 seconds, you're making some pretty good power. Just for kicks, lets say 500hp. That's what, 650-700cfm? Since you're just using a fraction of that out of the hole, 200cfm, that still passes the volume of the intake system in…

0.418ft3 / (200ft3/min x min/60sec) = .125 seconds

Now reduce the plenum volume to 2L -> .347ft3 -> .104 seconds

So there's some crude calcs. Question for you guys out there with big manifolds: How much of a difference does it make at the pedal?