It is true that the only way to permanently clear the DTC is to eliminate it via reflash. That's how the track pipe boys do it. Welding a cat in a near stock location is next to impossible because the stock cat is actually integrated into the exhaust manifold. I have a high flow cat in mine, but I'm not running any o2 sensors. I had my tuner take out the codes, and I have not had any issues at all.