And for good measure, a friend provided additional insight.

The potential HP gain associated with upgrading this / or that / or the other thing is deponent on the ability of the remaining components to keep up.

Thus, the potential HP gain from going to higher flowing injectors AND higher pressure on the regulator is dependent on the air flow of the system to more of an extent than the other way around.
~ Potential increases from better air flow are less dependent on fuel injectors until you start getting in to big mod's
Like a stroker would want a 24# injector with the increased fuel regulator to feed it.