It is simple. The problem described above would be happening whether or not he has a stock intake on or a CAI. As long as you hook up the breather hose and the temperature sensor as per the installation instructions, you'll be fine.

Since it sounds like you're new to this, here's what I learned (quick explaination):

- the temperature sensor in the intake senses the intake air temperature and is used as one of the parameters by the ECU (car computer) to estimate the amount of O2 (oxygen) that's going into the combustion chamber so it know how much fuel it should mix with it
- the breather hose is needed because air pressure can build up in the crankcase area of the engine. The pressure comes from several things, the main thing because "blow by" of the combustion past the piston rings. This pressure needs somewhere to go so a breather hose is the vent. However, since this contains unburnt gas and oil, it is an environmental polluter so the hose is routed to the intake so the stuff can go back through the intake to be combusted.