i've heard that the HO inlet has been flow tested by someone in the with a great manifold on his shelf too. and it showed that it did very well, better than a rover one did by a mile.
the only issue really with the HO is the long runners and the bends, port wise they are fine.
i need to get mine on a set of rollers as i believe i'm well over 320bhp, especially at a BAR and a half on the t04b bb turbo i was running.
i can't say how well it does up the revs with bigger boost, but no reason to doubt the torque it can produce even if there is a little drop off at the very top end of power.