<VV> air filters VS rich VS lean

[djtcz@comcast.net]

> snip................ Increasing air flow 
(besides increasing contaminate flow) does nothing but lean up the 
mixture unless you have a corresponding change in the fuel 
supplywww.corvairunderground.com

The bowl vents on cars and smart motorcycles go into the air cleaner to keep the pressure above the fuel in the bowl the same as the pressure at the carb throat.  This does wonders for maintaining air-fuel ratio regardless of air filter restriction.
There have been multiple  reports that famous tuners running bikes on dynos determine whether to go rich or lean for more power at a particular instant by restricting the bowl vent lines (leaner) or gently pressurizing extenal bowl vent lines (richer).  Way quicker than changing jets once just to know which way to go.