Just a heads up from my experience. Those cats arent cheap at all. I paid almost $900 for them from the dealer when I ruined mine off roading. If you decide to replace the o2 sensors, DO NOT BUY AFTER MARKET sensors, buy OEM directly from the dealer. Trust me on this one. It will save you the headache I had. After market o2 sensors dont work on our XK's. Also dont try to tackle to swap by yourself like I did. Have a buddy help.