correct me if im wrong but i think you would make the extra hp from efficiency not more volume of air. if your new turbo is more efficent it would make less heat at that same psi which in turn would make more hp. the volume of air is close the same naturally aspirated as forced induction. if you have say a 350 cid engine it at best can only take 350 cubic inches of air per cycle. but if its compressed air it is the same volume but more oxygen per ci. that is where you get your power from. if you take away the variables of forced induction like efficiency and friction all motors would have twice the power at 14.7 psi, three times at 29.4, four times at 44.1 and so on. what im trying to say is unless you upgrade to better efficiency or less friction you are going to have the same power at the same psi. the power you make is directly related to a combination of cubic inches, volumetric efficiency and psi.