I just put a CAI into my EJ8 and there was only a hole for the breather hose so I'm trying to figure out what this is and if its necessary to have connected. I unhooked it and left it out and noticed no difference in the short drive home from where I installed it. It goes in right next to the breather hose on the stock intake, sorry for the really crappy pic. Motor is a stock D15B.

 

Yes, you need the IAT sensor connected and installed in the air intake. It measures intake air temperature and is used by the ECU to determine the correct fuel trim.

 

Awesome thank you very much :]

 

You can probably easily just drill a hole in your new intake tube for it.