Originally Posted by juddz

...you can also gut the mini cats (fronts) and keep the ECU from setting a fault code by soldering in a MIL eliminator. I did this on my previous ride, and it worked out beautifully. You may know this, but the front O2 sensor before the cats actually measures and adjusts A/F. The downstream O2 sensor is just for OBD purposes (i.e. making sure the catalytic converters are converting unburned hydrocarbons and CO to CO2). Therefore, if you modify the output of the rear O2 and make it "lie" to the ECU, then there is no negative impact on engine performance and no check engine light. If interested, let me know. I can point you in the right direction if you want more information. Oh, and BTW - it did make a nice difference in my Mazda!