The amount of mass moved through the motor doesnt change the efficiency, increasing the rpm sure sucks more mass but not more efficient. Only increasing the temperature of the motor does or decreasing the intake temp. Thermo stuff. Its such a small modification i doubt it opens much up however thats what your maf sensor is for. Your car will automatically adjust fuel if more air flows in up until a point. Exhaust alone is not close to this point i think.

I am by no means an expert with this stuff. Grain of salt