So....wish I would of read the posts about K&N's before having one put on! My new Eco has less than 3k miles and kinda noticed the mpg was down, Eco had some surging at certain speeds and tailpipe looked a little sooty? Don't know what the norm is for these motors but after reading the posts and then reading this study: http://www.dieselbombers.com/chevrol...r-testing.html
I replaced it with OEM MotorCraft filter. Eco seems to be much happier and mpg has improved and surging is gone after 50 miles of driving. If you woulda told me an air filter could make that much difference I would thought you were blowin smoke!!
p.s. carefully cleaned the MAF to get rid of any oil left by the K&N as advised.

So...got a brand new K&N if anyone wants it!!!