I think (IMHO) that the tire pressure, engine break-in and then the K&N help fuel economy in that order. I don't think the K&N helps until about 2500 rpm or higher. At 70 in my 05 I run at 2000 rpm. So no help from a K&N.

Drive conservatively, keep your tires inflated and reduce air drag and weight of your vehicle will optimise your fuel economy. Intake and exhaust add-ons don't help that much.