CAI = Cold Air Itake....you'll see this abbv in many places. There are a number of intakes available for our v6. AEM, Injen, and CPE to name a few.
They all boast of gains, but I'll get to that in a second.
The AEM, and Injen are very likely to throw Check Engine Lights (CELs) without the CPE fix.
The CPE (Custom Performance Engineering)
http://www.cp-e.com/ intake boasts of the biggest gains, and comes with the MAFCi box which needs to be attached to the ECU.
If you are worried about warranty's you may be very leary to be playing around with the ECU, however it would be required with the other intakes as well with the CP-E fix.
I myself have the CPE (it costs about $500 USD new), and love it. I have no regrets whatsoever.
People have done many dyno's and comparisons between different brands and the CPE always comes out ahead. It's just made better.
It's an expensive starter mod....but its a great one that ou are sure to be happy with.
Remember we are only talking about 20HP...which is a lot from a simple mod, but keep in mind its not a HOLY CRAP I CAN'T BELIEVE THIS MY CAR WNS THE STREET.
...its a mod that will certainly make you smile, will make you happy with throttle response, and will let you feel it pull a little bit harder.
Its a mod that youll like and be very happy with without dropping a ton of cash for a turbo, or the like.