Originally Posted by undrgnd

^^^ Smog tests are not optional, but there are MANY ways to pass them with test pipes, depending on where you live. In my state, emissions testing means no OBD2 codes. They don't check your exhaust or do a visual. But even if they did, I would slap the OE cats on for one day and have it checked. Not too much trouble, every 3 years. A lot cheaper than HF cats, they don't wear out, and they have better performance, even if it's negligible.