I'll have to disagree. The only way to make more power is to move more air and fuel through the engine. Any kind of boost (N2O, turbo, or blower) will move more air and make more power. You really can't exceed 100% volumetric efficiency with a normally aspirated motor (yes, except with highly tuned induction and only in narrow RPM ranges). You CAN exceed 100% VE with N2O. Ultimately, the max available power is a function of VE, displacement, and max RPM.
that's only on race engines. most engines can be built for a high VE naturally and don't need NOS. many people build an inefficient engine and just add NOS to make up for it. or they build everything to handle NOS but could have gotten the same power by building it with the higher compression and efficiency for the same money. on race engines that have already been built to the max i can accept NOS but not on a street engine.