You hear and read so much on this subject that I am almost at the point of beleiving and saying that it is simply a 'variable'. What I mean is, doesn't it really depend on the 'nature' and application of the motor in question? Example, a low hp/rpm motor will need less and a high hp/rpm motor will need more,BUT,only if they are driven 'that' way, low rpm only,or high rpm only. Sometimes, 'application' is the determining reason. But a carb that varies and exactly fits the application of the moment,whatever it may be,,,,does it exist?