in california, you cant have long tube headers or modififed/bypassed emissions components. you can add aftermarket cat back exhaust systems. also, your check engine light must not be tripped on when going for testing. long tube headers will fail a visual inspection, and since they delete the catalytic converters, they will fail.
so you must have stock or short tube headers, at least one catalytic converter per exhaust path (at least 2 on your car) and then the metered exhaust must be in a certain range.
we dont have emissions where i live, so i have what we call "off road" exhaust where i have long tube headers and no catalytic converters.