Well I already have the drop in K&N air filter. Still only getting a meager 14 mpg so I decided it was time for some modification. The XK air intake system is crap there is a plastic plate covering the intake as a deflector for air. So I basically took it off to allow air directly into the airbox like it is on my XJ's. I am hoping this will net me a few more MPG. Will update results once I find out.