True engine porting has to do with both timing and fuel delivery. Quality engine porters can make a night and day difference between stock and hand modified engines. That's why they will do circles around stock engines and still manage to have better fuel economy. Also in some cases the powerband's characteristic can be drastically changed depending on the application, you might want more torque, or just a real peaky top end.

If all you want is to put more fuel in the engine, don't ever wonder why your fuel economy sucks.