"Overstuffing" in a personal watercraft

This is my 1st post. Excellent forum with some class act answers. I am trying very hard to understand this concept. I hear tales of getting to much water in the intake gullet at high speeds (70+mph and over), and this causes a speed loss because it puts a load on the engine due to "overstuffing". Later, and on other forums I read that not enough water is actually getting into the intake gullet because water cannot make the sharp turn into the gullet at high speeds. I understand that each pump has a curve that allows a pump to operate at it's optimum, but I cannot seem to tie these concepts together. What is the truth, what is the hype?

There are many modifications to make PWC go faster, mostly engine mods with a few hull mods. I have read of no such modifications on the intake gullet. How does one go about such a thing? Bottom line: How do I make the pump, intake,impeller and venturi operate more efficiently as a unit?