Save yourself some money and buy O2 sensor blocks. These make the computer believe that it has O2 sensors. I would only do this if the sensors are for the exhaust and not the intake. For the cats, you would not need to replace them if you do not want them because of the O2 blocks make them believe that cats are in place. If you really want new cats, go on ebay and look up 2 inch catalytic convertor. That should give you an idea where to start.