Not entirely true, the design between B16a and the Type R manifold determins your peak power curve in your rev range.
The type R and most aftermarket manifolds are made to make the most of type R and aftermarket cams, as they have shorter but wider runners , witch make there power curve right up top in the rev range 7500-9000rpm. Where as in fact the b16a manifold gives a better power curve upto 7500rpm over the type R, but then the type R overtakes as it peakes higher up. As the B16a manifold has longer but thinner runners.
Its quite intresting to swap bettween b16a and Type R manifolds on the likes of a b18c, as if your spending alot of time between 5000-7500rpm then id say with the b16a manifold it is more useable.
I did have a dyno graphs of a B16A mani against a Type R on a b16a and b20Vt but i cant seem to find the link to it.
Thus why i tried my b16a mani on my b18cR to see and it deffinatly feels more useable upto bout 7500 but kinda trails off, where as with the Type R it keeps pulling and peaks higher.
Sooooo my point is for a street b20vt likely with a rev limit round 8k id say the b16a manifold would be best suited. BUT!!! i would still bet those figures of 250hp is total bull. As with that mani and full standard airbox. power would peak to early would never reach those peak figures.