ah yeah i know this car....its currently for sale >
http://www.carsales.com.au/all-cars/privat...id=123AB1F0900B
CAI shouldn't set you back too much you just need the material to make a surrounding for the pod filter, or alternatively you could buy one pre-made.
check out r31skylineclub.com, i remember seeing a DIY section for cold air intakes and photos of everybody's different designs etc..