State laws for aftermarket parts?

For the job feild I'm going into I have something like a 86% chance of being relocated out of state. Witch I don't mind because I've heard the laws are more lax outside of California when it comes to modifying your car with turbos, exhaust systems, etc. But I was just wondering what's so different? I know in calfornia all the laws pertain to smog, so are the smog laws different? If I could get some examples that would be great... I don't know exactally where I'll be sent so any and all states are fine. Thanks