I have a 97 cx hatchback, which is 100% stock. That’s due for emissions testing soon. The check engine light came on, so I took it to a shop and they checked it with the scan tool. They told me that the cat was bad. The guy disabled the cel, but it came back on after 3 hours. So I called auto zone and they want $800 for the cat. My question is if I get a stock or after market header for my car and a stock dx cat (which is only $130) is there any problems I might run into besides extending the O2 sensor wire? Will the exhaust have to be modified? Any help would be great and thanks for your time