it's not carbed, you have the E16i, unless the car is from mexico or canada or something like that, you've got TBI(throttle body injection) with a single injector in the throttle body. The first thing you can do is take some of the restrictive piping off of the air cleaner and flip the lid upside down, there is also a K&N filter made for your engine. There's also a throttle body swap that someone's working on in conjunction with a CAI from a Dodge(
http://www.nissanforums.com/showthread.php?t=34023 )
And a little searching can go a long way. Oh yeah, welcome to nissanforums!