Im in San Antonio and i passed no prob with a prochamber, know tons of people with o/r pipes that have no probs either.
Just don't go to some big shop, the little shops almost never care..... I went in with my SES light on and everything, the guy just turned it on, revved it a few times, told me it sounded badass and gave me my sticker. $12 too.
The more ghetto the place looks, the better.