I don't believe you can get any noticeable improvement in MPG or POWER by using a K&N filter, but what you will get is more dirt in your engine. Look up some of the engine air filter tests online.Not so much noise, but if that's a side effect, I'll take it. I'm really looking to increase performance and mpg.
With a modern computer controlled ignition and fuel delivery system, even a fairly dirty air filter will barely reduce the mpg, but it can reduce the power somewhat under FULL throttle.
Buffalo4
PS