What tire size are you running?

I recommend a skinny tire at max air pressure for optimal MPG.
Keep the windows up and A/C turned off.

You will get lots of opinions on K&N air filters and some of those offering opinions have even used K&N's.

Personally, I use K&N air filters and Lucas Fuel Treatment bought at Wal-Mart or auto parts stores. I consistently see ~1.5-2 MPG increases for each, so about 3MPG increase using both. My wife's Mazda MPV van really benefits from the Lucas.