I have a 98 civic coupe that I just put a b18b1 in, what do I need to make the exhaust work, right now I have the stock b series exhaust header and some random aftermarket exhaust. They do not fit together. Do I need to get a whole new system or is there a simple part I need? Thanks

 

You need a cat converter that mates to both sides.

 

Where should I get one of those?

 

An exhaust shop can put one in for you.