Not sure about ozzys fuel theory. I am pretty loose with my fuel
But he is right about the spray bar position. But basically the mid end needle effects the acceleration point from about 5-20 feet when you nail the throttle from a standstill. The first 5 feet are all low end, the next 15-20 are mid range then high end needle. Trying to feel the difference at partial throttle requires much more experience than I have so I never play with it on my engines. It can give you a bit more mid corner punch if done right.