I haven't noticed much of a change at all. ?Maybe a bit more sound at WOT.
I don't understand how an airfilter can improve gas mileage. ?If you think about it, a better flowing airfilter is essentially the same as opening up the throttle a bit more. ?I adjust my foot's pressure on the pedal to achieve a desired cruising speed, and the computer controls how much fuel to add to a given airflow that I am controlling. ?I would think that it is possible that a better flowing airfilter would give more power at WOT, since it would make wide open a little more wide open, but other than that, I can't either theoretically or emperically tell any different.
Throttle response may be better, but I haven't been able to detect it with the seat of my pants.