It's weird to me how I have to smog my car every year but by simply having no CEL, I pass every time. Meanwhile in CA, they put the car on a dyno and a sniffer and only require it, what, every 4 years? Jee, I wonder which one is more effective?
FWIW, my stage II car made zero gains when I went to one step colder plugs and replaced the stock 3rd cat with an expensive Crucial hi-flow cat. Ed was up here tuning so I had him retune it after these mods and I ended up with almost identical HP and torque as I had the previous time he was up and tuned me. I'm sure my full 3" exhaust is also overkill for my current power level.