I"m thinking about doing this too, but will doing this trigger the Check engine light to come on? Or will I have any other problems, like with an O2 sensor? Thanks

 

when i had my PCM tune done, i had them write in for removal of the cat. haven't taken the cat out yet, but didn't want to until i had the program in. otherwise it might run rough. you need at least the muffler to keep backpressure up, especially in a smaller sized n/a engine, IMO

 

If your car is 1996 or newer I would leave the cat alone or at least get a high flow cat. There are o2 sensors on both sides of the cat on OBDII cars to detect the effeciency of the cat. if you core or gut the cat or remove it you will change the exhaust flow and mess with the sensors and get a CEL or other drivability issues. I cant remember the code number but the definition is Catylist effeciency above threashold. you may also get downstream O2 sensor issues. as well. A high flow cat does not cost that much HP and you will prolly not even see a difference between HF cat and straight pipe. Your call. Oh and the removal of any emission equipment is illeagal in all 50 states, no mater if the area you live in is exempt or the car is exempt. To remove the emissions from a vehicle will make the vehicle an "Off Road Only" vehicle, meaning you dont get a license for it.

Massey

 

you can tune the rear O2s out, all they do it set a code to say the cats are not working, just have to code set to not reported etc and no MIL light.

I don't know about you guys who say it doesn't change sound, but man it DOES, it maybe a little more raspy and obviously a bit louder and the sound will be different up the rev range and under load. Have you every looked at a cat inside, try putting a light at one end and looking through the other, come on if it blocks that much light, how much more of a restriction to exhaust flow is it