OK I've finally come to a conclusion on which intake to get. I'm going to purchase the AEM Cold Air Intake. The actual question that I had was about the Bypass Valve; what exactly does it do, and do I really need it when I purchase the intake?

nice choice on the intake, they fit perfectly. but on the bypass valve, all it does is stop water from entering the throttle body. some say that you need it others say that you dont. I personally think that you dont, unless you are going to drive around with the filter submerged in water. The best defense would to keep your fender linings.


Ill make a sig someday

I got the AEM CAI, love it. I didn't get the bypass valve as i thought it wasn't needed. I've driven through some pretty hard rain without any problems so I wouldn't get that. Keep the inner fenderwell covers and unless you drive through water 18" deep you won't need it. My only gripe with the AEM CAI is it's not easy to clean the K & N that comes with it. You basically have to take the inner fenderwell cover off and re-install. But aside from that very small item it's great for the money. Fairly easy to install in an hour or so and you can actually hear the air rushing in when you punch it. I got mine from Aaron, at Turbo Tech i think.
Don