I'm considering doing long tube headers, and I want to keep cats to keep the computer and the law happy. I want them to flow as good or better then the stock ones, but also not trip any codes on the computer so I do not have to worry about having it reprogramed. I have heard that some of the replacement cats do not work the same as the stock ones and the computer sends a code. What brand/ cost have you guys gone with and what works/ doesn't? I would be modifyin the stock y-pipe adding probably stainless tubing before the cats.

 

if it has high milage then you can change them. i used carsound cats from magnaflow. they worked great and are around 50.00.