will a exhaust system including headers hi flow cat and cat back exhaust for afour door1997civic ex be a direct fit for myfour door1997 civicdx if not what modifications well this swap require

 

actually i think it will. The DX has the cat built right into the exhaust manifold/header and the EX has its cat right after the header, so if you were to get an EX catback on a stock DX header it would be too short (since it needs to be shorter to bolt up to the EX's cat), but if you are gettin a bolt on cat to go right after the header, i htink it will match up the EX catback just fine. They're both D series and they're both sedans, so im pretty sure everything will work out.

 

as long as you make the entire change from the DX layout to the EX layout, it will fit.

You will obviously need all of the above mentioned parts, including necessary gaskets to do so, in addition to extending the O2 sensor wires to be located near the appropriate places

 

thanks for that, yea the secondary sensor won't reach the new cat. You'll either need to extend the wires (which is easily messed up), or get an o2 simulator from www.o2simulator.com to cure the CEL you will probably get