So maybe this is obvious, but the Civic DX has the Catalytic Converter attached to the header. So I guess my question is ifI wanted to replace the stock header with a new one,I am required to install another Cat someplace else or purchase a catback system. Am I correct in this thinking? Thanks.

 

good thinking man, i got a DX too and was in the same situation. Get a header from a d16y8 (99 EX), and then buy a high-flow catalytic converter etiher from Randoms-Tech or Magnaflow. Get the cat welded into the exhaust system anywhere (usually towards the front, before the resonator) and you will be all set. still stay emissions-legal and also get some new perfroamcne