Well, I got my K&N CAI kit for my truck. My brother and I put it on. I think it makes more of a difference @ midrange speeds. I got the 57 series. I like it so far....

 

what about gas mileage? have you seen any difference?

 

Lets put it this way, i never really checked the gas mileage before i installed the K&N, but last week and weekend, i hauled my boat twice to the lake, did alot of stop n go yard sales, and of course after we installed the K&N, my brother and I tried it out to see what difference it might make, and in midrange, its noticeable and if ya tromp on it, ya can definately hear the K&N drawing in the air, so we really didnt drive like i normally do so that being said, i took the gas mileage this past Wednesday, and i went 277 miles and used about 18.5 gallons of gas which equals out to right around 15 mpg, so driving normally and maybe a trip here n there, i should get around 16-17 mpg, which isn't half bad. Eventually, exhaust work will get done but will let this exhaust rot off first chances are.