I think that all Euan is trying to say that if you increase the capacity at the same time as improving the flow capability of the head and the turbo, that the power goes up by "around" the increase in capacity.

Everyone else seems to be taking the stance of limiting the increase by retaining certain limiting factors . But to be honest, you would have to be REALLY stupid to retain these limits when increasing the capacity. Obviously the norm is to take advantage of this extra air flow with a bigger turbo etc....

See that was easy, you just have to see it from BOTH sides .