CA emissions w/ no cat?
Technically removing the cat is a federal offence. but its only so on street cars. Track cars (non-registered with DMV) don't fall into the perview of that law.
Your not gonna pass any cali inspections without the cat. also the replacement must have a CARB number on it.
(by the topic im and guessing your in California.)

as far as federal offenses go.. i dont think having my car sound loud as **** is worth... one hundred billion dollars ::dr. evil pinky::
i think ill just go with a racing cat and a cutout
although i wont be smog legal i still will have a cat on so i wont have the FBI on me lol

