K&N just lets more dirt into your engine. I had one of their drop-ins and you could see daylight through it when you held it up to the light or sun. AFE, S&B and volant are good ones. I agree with nOuseforaname....if I knew what I know now, I would have saved the $300 for a different mod. I haven't noticed any gains with my intake, just a louder turbo whistle....which is cool and I like it, but I could have used the $300 elsewhere on the truck.