About the pilot jets:
The reason that these should be selected so that you get the best idle at 2 3/4 to 3 1/2 turns on the idle mixture screws is that they feed more than the idle jets. On the airbox side of the throttle plates, there are 2, maybe 3 holes drilled into the same passage that feeds a gas/air emulsion to the idle jets. As you crack open the throttle, these holes feed gas to the engine untill it is running fast enough to pull enough air to open the slides. It looks like these 'transition' jets come into play again when the engine is running flatout with a heavy load to provide the same function as a power enrichment circuit on a car/truck carb.
So, let's assume a bike is on a good dyno with an accurate air/fuel ratio gauge. If the mixture is off starting around 1500 and starts getting better around 3500, chances are the pilot jet is off size. If the mixture is off above 3,000 and straightens up by 4,500 you probably need to add or remove needle shims. If the mixture is a little off around 3,500 and gets worse as the engine speeds up, you need to change the main jet or change to a different needle taper.
