Injen Intake on my friend's 350Z is quiet
 

My buddy has an injen cai on his 03 Z and it make no intake noise at all. No growl, not even the suction noise. My frankencar sounds way meaner. What's the deal or what do you guys think about this.

CAI are not that loud, they are farther away from the engine and barried in the bumber so u will not hear them, your franken is a mid pipe correct? If so like mine the filter sits rate near the crack in the hood and the fender. So u will hear it alot more. Thats my educated guess but I could be wrong.