GA (Metro Atlanta area) only does the pipe test if your car is not OBDII compliant.
So if you're 93 or older (I believe), then you gotta do the whole test. If you're newer, they run an OBDII check and if the car's computers says you're good, you're good!
Cars past 25yrs old and Diesels are exempt.
Outside of Metro Atlanta, there's no emissions law at all.
I'd never run catless. Even if it weren't policed. I hate the raw smell and I'd feel bad about destroying the world just a bit more so I can get an extra few ponies.