[priobe]

Well,

When taking a fixed number on your idle fuel jet, say for example 60 (fuel) you will have a leaner mixture with a 120 holder ( that introduces air) versus a 100 or 70.

Also remember that the at idle you can have a good fule ratio but once the throttle plates open you will receive additional fuel from the pump jets for a specific amount of time. If you are driving with a steady pedal you will not receive the additional fuel from the pump jets. Most people like to run 00 exhaust valves to dump alot of fuel with the intial depress of the pedal. I would rather tune with out the aid (if possible ) of the exhaust valve. This is why my exhaust valve is set to 55.
I hope this answers your question.