The best part about a CAI system isnt the POWAHHHH that you get (woo- 2rwkW if you're VERY lucky lol), its the ability to run a damn-near unrestricted flow path for ambient air, assuming you put a large free flowing filter panel or pod in your airbox.
Means that when you stomp the throttle at idle, when rolling along, whenever- you'll be getting colder air than you would from a stock setup or (god help us) an under-bonnet pod filter/hot air suction machine. This generally equates to a snappier throttle response, a few extra Nm (which is where the rear gains are) and a full hektik noise.
i ran a 90mm poly- pipe CAI setup on the wagon on the wagon for a few WSID runs, was all sprayed temp-proof black and with no other mods i dropped 0.5 seconds on average on all my runs. 60ft times (while crap) was where i got my gains. Gained 1mph