I just purchased a 2008 Z, and I bolted on the Injen True Dual CAI. I am definitely not new to the car modification world, but I am experiencing a gurgling/rattling noise under the right side of the hood at 1450-2000 rpm's that I have never heard before. It is most apparent at 1750, and I have no idea what is causing the rattling. All the bolts have been tightened thoroughly, and I cannot see where any metal on metal rubbing could be occurring. My only educable guess would be that the exhaust tone in the specified RPM range rattles something in the CAI system. (Not unlike a subwoofer rattling parts of the car at some frequencies and not others.) Admittedly, I have only worked with short ram CAI's, but I really cannot see what is causing this/how I screwed up. Anyone experience this? If so post please.

(Also, the sound occurs at no other RPM than the ones I mentioned above.)

Thanks for the help!

 

One more thing: the rattling only happens between 50% throttle depression and WOT.

 

I have these also and do not have the problem that you are having. Can you post some pics of the intakes installed, maybe you did something wrong... Not sure what could rattle.