I was just at the Delphi board for Kawa Vulcan 800's today (researching for a buddy of mine). One link about carb mods said not to bother doing an air box mod unless you freed up the stock exhaust! Sounds about right to me.....
As for the CV carbs working better with the restrictive intake box, the cure for that is the 7/64's inch drill-out of the slide hole.
