I've read, never tried, about the O2 sensor spacer trick to fool the ECU into thinking the cat is working properly. I have a Magnaflow system on my car with a high flow cat and I have a P0420 code. My first question is has anyone done this trick and not experienced any problems afterwards? And my second is how will this affect my car during the state mandated emission testing to register my car for new tags? Thanks in advance.