the mileage has the potential to increase noticeably, but chances are, youll like the sound of the new intake at wide open throttle too much, and youll get about the same as before.

 

get a CAI anyways. preferably the AEM, i know AEM markets a valve that closes off the main part of the intake should water get into it and diverts the air intake to another part of the pipe. Some magazine or something did a test on it with the valve installed on the intake and fully submerged the filter in a water tank. it took in no water at all. seems like a very good deal to me, ive never found one online but ive never really looked either. i will try to find one and post a link if youd like

 

The bypass valve is what you are talking about and they do work. I live in Ohio and had a full AEM intake with bypass valve installed on my Eclpse and it saved me a couple times. IMO the ebay cheap CAI with a K&N filter installed and a bypass valve is the most cost effective setup.