im doing it on my singlecam, the plenum im making for the ITB manifold has 4x the volume of stock, the "runners" from the head to the plenum are about 1 inch shorter, they are also a bit larger around, and the combined throttle body surface area is a little more than double from a stock Z6 throttle body.

should get better throttle reponse, more flow, and (relatively) faster air speed b/c of the velocity stacks.