Last tank was +2 MPG after installing the K&N filter. Considering the average temps (105+), this is huge. Went from 27 MPG to 29. At this rate, the air filter will pay for itself before the end of the year.
It is the little things. Besides improved MPG, there is now a little bit of noise coming from under the hood and the engine has a little bit more to give. /me thinks it might be time for some mountain testing.