your exhaust setup probably (like 99% of them do) has a resonator already built into it...theyre like in-line mufflers.
The ebay cats are junk...theyre more of a test pipe than anything and shouldnt be used in place of the cat. It will, almost definately, not pass emissions.
If you want one, I suggest catco or carsound/magnaflow. Both of those need to have flanges welding on them...which of course raises the price. These high-flow cats MAY pass state laws, but you should call up your state ref and ask first.
No, it will not replace anything but the oem cat. If you look under the car @ the header you will see a bulged pipe (probably has heat shielding on it)...thats your cat. It is between the header and exhaust b-pipe. There is an o2 sensor inside (which would need to be added if you went w/ an aftermarket unit from carsound/catco)...which still may cause some to throw a cel because there is a lot more flow through the aftermarket, thus giving a reading that would be off from stock. -> O2 simulator or OBD1 conversion would fix that
|