From what I've heard over 10000000 posts regarding cold air intakes, here are my findings based solely on power gains:

Mugen >> Comptech Icebox/AEM CAI/Injen CAI >> OBX/Arospeed/Pep Boyz

I wouldn't shell out the $$$ for the Mugen, but any of the setups in the middle portion will do just fine.

Shingo