Do you guys change your O2 sensors as soon as they set a code? It is getting expensive to replace them after every track visit or if I drive on the street for a little while. Since the ECM doesnt use the O2 for WOT fueling, can you just leave it in there even though it has set a code? Will it cause any problems? I know that if you use a fresh O2 over a burnt out O2, you will pick up .1 to .2 in the e.t. Thanks for any feedback.