[RossBMWZseries]

Originally Posted by pokeybritches

I thought California got rid of the sniff test?

I have OEM U.S. headers and S-pipe I could let go if you're interested.

Your description of the stock exhaust is correct - the S-pipe and section 1 are the same piece. The stock U.S. exhaust has four parts:

1. Catted headers (this is where the primary and secondary O2 sensors are. The car you're looking at has catless Euro headers, so the secondary O2 sensors (the ones that used to check catalyst efficiency) have to be move into the S-pipe to avoid a check engine light. The car's computer must sense a cat between the primary and secondary sensors.

2. Catted section 1, or S-pipe. The DKF system replaced this component with a much better, free-flowing system. The OEM U.S. section 1 does not have O2 sensors. The Euro and DKF do. DKF is the least restrictive of the two.

3. Resonated section 2, or X-pipe. This is a crossover to help with exhaust scavenging and improve sound. It sounds like this system is stock on the car you're looking to purchase.

4. Mufflers, or section 3. The main reasons people swap these out are for sound tuning and looks.

If you went back to the OEM U.S. setup, you would lose 20+ horsepower and a lot of sound. As long as the car isn't throwing a check engine light, you can pass emissions (assuming no sniffer) if your guy gives you the thumbs up on the visual.

The DKF cats haven't been proven to pass or fail emissions. There's not a lot of data out there... yet. I have a theory that it's all related to cat temperature. The people passing have ceramic coatings or forced induction. The ones failing do not. At the same time, my friend with non-coated headers has put his 300 cell cats in and had no CEL, so the jury is still out.

Corrected