Yeah that's Japlish for air corrector. As air velocity rises in the throat more fuel is dragged up through the needle jet, if there was no air corrector, the mixture would go ever richer with rpm(the downfall of Lectron/Ei carbs). Enter the corrector which adds air in proportion to the amount of air going into the carb.So if your having low end rpm problems the air corrctor isn't the place to look. It's the slide cutaway and idle mixture screw that give air to the low speed circuit.
There is no real 'correct' jet for this just remember the smaller the jet the richer the mixture(taking away air), as I have a VM36 that had no corrector jet and has been drilled out a bit. If it is running well then that's the correct jet.
Has the engine got low speed running problems?