Let me put it this way... with a test pipe YOU WILL NOT PASS EMISSIoNS!
Do you want to change your exhaust every year to get it smogged, then put it back and risk getting a ticket becuase you car smells like ass and is polluting the environment?
Or... Would you rather put on a Car Sound cat that flows almost as well as a straight pipe in tests and not have to worry about it for a long, long time?
The choice is yours. Oh, by the way... Have you every been to L.A. (or most other large cities) when the sky is brown from smog and you feel like you are gonna develop Asthma just by looking at it? In case you don't get my drift, smog looks like this: