I recently bought a 2004 F4i, it has what appears to be a slip on. But there’s an o2 bung on the pipe without an o2 sensor, and the bung is wide open, not sealed. I’m not getting any warning lights.
my question is should there be an o2 sensor? I live in PA, I’d imagine the bike originated on the east coast. And, if there’s not meant to be an o2 sensor, should I seal up that bunghole? The bike seems to run just fine as far as I can tell, but I’ve never ridden one prior to this one.

 

Your exhaust fits models with or without the sensor. Since you're bike didn't come with one, plug the hole with a bolt and a crush washer.

 

will do, thanks. So, if I understand correctly, I’ve pieced together From other threads that models from CA came with an o2 sensor, and the 2006 model from any state. Is that correct?

 

Sounds about right.