At what stage of N/A builds will the fuel mileage go down?

From what I can guess, once you move to a larger injector or increase compression you're going to start loosing fuel efficiency, also if you hog out the head a lot. Any thoughts?

On the other hand, I/H/E, mild head porting, or a cam shouldn't effect it from what I can tell... but increasing compression is causing more resisitance to the rotation of the crank, and typically larger injectors don't atomize as well.

 

To tell the truth on our engines loss in your milage will be slim depending on the tune.