I bought a pre-owned '97 Sierra 1500C which came equiped with a K&N Filter system which I have thought was state-of-the-art. I typically can do most of my own work, but recently had to take it to a mechanic for heavier maintenance. This mechanic tells me that K&N systems are now thought of as low performance items and that I should put the OEM filter system back on. Would this help my fuel consumption? Any comments?

 

K&N's are fine. i certainly wouldnt replace it with a stock filter or airbox setup, if the truck already has it. people give K&N a bad rep from the few that are too stupid not to overoil the filter after they clean it. overoiling causes buildup on the MAF sensor. just oil it correctly and all will be well.
the main thing for MPG is your right foot. i noticed no increase or decrease with the intake setup on my truck or the replacement filter in my car.

 

I second that!! Have you tried Tru Flow?