Most common place is between TB and IC. Also don't overlook IC's bottom side. Just take out the IC and reclamp the whole thing. Make sure all the clamps are not stripped.
you could build a leak tester. http://forums.nicoclub.com/zerothread/113785 another way to build this is to use pvc pipe and a pvc cap with the same valve. i am going to warn you before you use this. please make sure your air source is pure air and not a lot of condensation. dont want all that water in your intake. heres another http://www.vfaq.com/mods/ICtester.html
Just run outside and simply double check the connections (dont forget the air return lines on the right side).