im am going to be ordering IHE and i was wonder what kind of Cat i need for my car? i have a 2004 civic ex.
i was confuse when i saw CAT that are without air, and duel so i was wondering what Cat i needed thanks

 

no idea whats your talking about with "air" or "duel", but with I/H/E, the Intake has nothing to do with the cat, the header bolts right to the stock cat, and the exhaust goes from the stock cat back. Techinally, you really dont need to mess with the stock cat at all.