I put on some magnaflow high flow cats, paid about $125 each. The entire system with cats, muffler, resonator was $900 with labour.

http://www.magnaflow.com/02catalytic...niversal=54305

But being in Cali, you have a whole section for you:
http://www.magnaflow.com/02catalytic...niversal=45105

So assuming half off MSRP, roughly $300 each....

Mine lasted about a year or two. Some of the mesh interior blew out the tail pipes. Some of it ended up wedged in my resonators and caused some vibration noise for a week until it broke down.

I don't get any CEL from the O2 sensors.








good luck!