a Cold Air Intake is not worth it alone, however if you also get a custom tune to accompany the CAI, it so worth it.
that being said, a custom tune is also very worth it w/o buying a CAI.

but max gains off easy quick cheap bolt on's is with a CAI/tune combo.
the 4.6 and 5.4 are VERY responsive to these modifications.

 

Quick and maybe a stupid question, but where do you go about getting a tune if you were to get an air intake? Also could I not just wait till the middle of Nov. when the ghyro or however you spell it comes out since it is tunned for specefic mods, and then have no problems?

 

I recomend calling Chris Rose at Tillman Speed. They are Ford and Mustang specialists. They did wonders for my 08 mustang GT with the 4.6 He also tunes the 5.4

You can either buy a CAI and the tuner/tunes from them as a combo (they usually give you a great deal) or you can buy the CAI elsewhere and then just let him know that you need tunes for your truck with a CAI

www.tillmanspeed.com

VMP tuning and Troyer also provide tunes I bet you can even try www.brenspeed.com/
another mustang specialist, but they are used to tuning the 5.4s since they are in the current GT500.