Ok, the dual exhaust question has been beaten to death. As of late, I haven't read anything that would help answer my question, so here it is.

Say you've got your average inline-4 Honda engine, h23, h22, f23, b18, etc. Ok well more specifically, I'm thinking of a built H22a with a T03/T04, 1bar boost. Now say it's turbo'd and is creating some serious exhaust flow. What if you had a y-pipe with a valve in the intersection of the Y-shape, allowing you to choose which pipe was open at any given time. Then, the turbo would be plumbed after the y-pipe. Say, one pipe is a thinner diameter, for high flow velocity in the low-end and increased scavenging, and the other pipe is larger diameter, for the upper revs when the thinner diameter piping would start to cause too much backpressure. Would the thin pipe's ability to create a faster velocity in the lower revs help a turbo to spool up faster? And then, when the revs are higher, the larger pipe could feed all that exhaust into the turbo? Perhaps the switchover from the small to large pipe could coincide with the VTEC-cam engagement? Or would it make more sense to have the y-pipe and valve placed after the turbo?