I was told NEVER to get a K and N because they are oil based and suck too much oil and dirt in. Anyone on this forum will tell you not to get one. I've never heard bad things about Volant. There's also an AFE intake system that is suppost to be good. But then again..people who buy intakes normally say it was a waste of money and it just made the whistle louder. The Stock AC Delco is supposed to be really good as is. Hope this helped some.
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.
I have the Volant C.A.I. part#15066. It was simple to mount, I had to remove the stock mounting plate and a plate from the rad support(lacks proper instructions). The filter ( a proguard 7 seems like it is supplied by aFE...the recharge kit has aFE on it ) was a tight fit through the opening and one screw on the cover has to be installed with water pump pliers ( right beside the coolant reservoir). I can definately hear the turbo whine ( i like it ) and slightly feel an improvement in power. ( This could also be due to the pound of sand I dumped out of the stock filter when I removed it). The $359.10 was worth it for me as the replacement filter at the dealer here is $92 so for 3 1/2 of them, I hope to get many years out of this one by washing and reoiling it. Plus it looks sweet when you pop the hood.