O2s are in the same position as stock. Luckily we only have mechanical inspections here so I had the secondaries coded out anyway. Still have the stock SE cat-back exhaust. Sound is comparable to stock but with lots more turbo sounds. I don't know whether to attribute that to the lack of pre-cats or the entire downpipe. Cruising at highway speeds with the slightest throttle increase and you're greeted with the intoxicating sound of turbo spool.