CAI = Cold Air Intake. You could go to www.comptechusa.com and check out their intake under the Accord page. I just ordered their cold air box for $240 shipped. If you don't want to do the install yourself, a shop will probably charge you 1/2 hour to an hour to do it.

You can also get the exhaust, about $550-$600. With those 2 modifications, your cost with installation will still be under $1000. The downside to this is it will add "noise" to your TL. Not bad noise, just intake noise and exhaust noise.

If you are willing to spend a little more, get the Comptech headers. A shop in Florida is selling them for $999 shipped, but it will get close to 20hp to the wheels for the regular TL. A shop will probably charge you 2 to 3 hours to install it. The headers will not add that much noise, you probably won't even notice the extra noise but you will definitely feel the extra power.