I have a 97 hatch with a d16y7. I bought the car and the header had an exhaust leak from the upstream 02 sensor. The guy "fixed" it by welding it on there and barely sealing the crack itself. Long story short I had a friend of mine touch it up so I could pass smog Its not making that annoying exhaust leak noise as loud as before, its more subtle now. Regardless, I"m going to need a new header. THe only problem is that on the y7's the header and the cat are all one piece. The part itself, brand new, is almost 700. My question, could I put an aftermarket header (dc skunk2 etc) and subsequently install a cat after the header, would it still pass smog when I have to go get it done? I do live in Cali so our smog restrictions are higher than most states. I figure if I'm going to need a new header, why spend 700 on a stock piece when I could spend a little less and have a performance header and a high flow cat. Any input would be great.

 

If you posted this in the correct location.. i.e. the header and exhaust section you would have seen that the first sticky is a y7 to y8 conversion how to guide.

Header, Intake, & Exhaust - HondaCivicForum.com

allows you to run whatever header you want while keeping a stock cat which should help you pass smog in CA.