Don't bother with a CAI kit, they are a waste of money. Either get just a K&N filter, or a new mas-air sensor kit. All you are getting from the Mac and other CIA kits is a K&N filter and chrome to dress up the engine compartment. I'll copy my post from another forum:
When it comes to a CAI system, I would avoid any kit that uses the stock mass-air housing (such as the Mac cold air kit). The stock mass-air housing is the most restrictive part of the intake. A new K&N airfilter will add about 2-3 HP by itself. A CAI kit that uses the stock MAS housing provides the same HP gain so long as you are using a stock air filter. These kits are providing you with nothing more than a K&N filter and a fancy tube to replace the rubber hose. The kits do not provide any benefit above the stock intake with a K&N filter. If you want REAL HP gains, look into a new mass-air sensor kit. Check out C&L performance (
http://www.cnlperformance.com). Their kit provides 6-9 HP gain for a little more money and replaces the mass-air housing with a larger, 73mm piece. Don't waste your money on a CAI kit, just buy a K&N filter for the same HP gain or buy a real intake kit. I've got the C&L kit and it does work. If you are going to add a larger throttle body at some point, this kit will feed it more air than stock or a CAI kit.
Try this test for yourself. Drive the car for 30 minutes or more to get the engine nice and warm. Then remove the rubber intake hose behind the air cleaner and feel the temp. of the aluminum mass-air tube inside the air cleaner box. IT will be cold to the touch. So, if the MAS housing is cold when the engine is hot, do you think a CAI system is really isolating the air cleaner from the engine heat? If it is, it's not enough to make a difference in performance. Also, the mass-air sensor works in conjunction with the temp. sensor in the intake to determine how much air to flow through the throttle body. If a CAI is really providing colder air, the temp. sensor will adjust the TB accordingly, which will cancel out the effect of the colder air. The only way to increase air flow is to change the MAS calibration. The MAC and other CAI kits do not do this, but the C&L kit does.
Hope this helps.