Up until last week I had a high flow 200 cell catalytic converter attached to my 4-2-1 header via a doughnut connection. When I worked on my transmission recently I pulled the high-flow off and installed a used OEM cat that I bought from CL as I have my yearly inspection coming up that includes emissions. The high-flow in conjunction with a O2 extender worked well for about 6 months but then the precious metals must have dissipated to the point that even with the extender codes started being thrown. I have done allot of research on cats and aware of the "magic" dimension for long life and how the matrix folding impacts life span as well. With the high-flow attached to the 4-2-1 and the JCW exhaust I had a great tone and the pops/burbles were quite nice, not overly loud. Back to the O2, it does not really sense oxygen levels but rather the temperature of the exhaust as it exits the converter. If the engine mixture is rich then there will be more fuel, hydrocarbons, and the precious metals within the converter matrix will "burn off" this excess via a chemical reaction that creates heat. More unused fuel in the exhaust, the hotter the post converter exhaust stream. A lean fuel mixture will have less unused fuel so the the post converter stream will be cooler. I am thinking that if you know what impedance range the ECU is looking for a resistor in conjunction with a capacitor may do the trick. Something like the picture below. Anybody had success with this?