I found that the sound with the AirBox mod to be a little deeper and more throaty than with the Injen CAI. I definatly enjoy the sound of the Injen CAI when accelarating, but IMO the AirBox mod sounded just a bit better due to the deeper sound, but the Injen is prolly louder.
If you get the Injen make sure to contact CP-E for the MAFci fix