Mikuni needle jet

A single carburetor should give almost the same power as twin carbs. And better if you tune it right. It is not power above certain revs you should be concerned about, but power at various throttle openings. If the needle jet and needle are correct and the main jet is slightly too large - you should get good power at all throttle openings, regardless of the revs,( unless you have a race cam fitted - then you might have less power low down in the rev range.) The problem of finding the correct needle and needle jet is difficult, if you don't have the next smaller needle jet available. When you lower the needle, you should be able to force the motor to cough due to leaness - then raise it one notch. I would use the largest specified main jet, at least while tuning.
A restrictive air cleaner can kill top end power. But you should be able to tune to suit it.

pete.v said:

P8 is standard. Q4 might be a good compromise.

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Setting the idle is easy. If the adjusting screw leans the mixture, you just start the bike and get it idling. Wind the screw in until the motor misses, then wind the screw out slightly until the idle becomes smooth. You should never have black smoke coming out of the exhaust. If you cannot force the motor to miss, you have a jet somewhere which is too large. If the main jet is slightly too large, it usually does not matter, but everywhere else, too rich makes the motor sluggish.
A lot is in the mind - YOU are in control.