My cat's insides fell apart last time I was at the track and they took out the rear O2 sensor with it. I now have a replacement cat, but it's taking way too long for the replacement O2 sensor to get here, and I'm worried it might not make it here before my next track weekend.

I assume that the rear O2 sensor is just there to make sure you have a working cat. Will there be any issues with me running the car at the track with a bolt in the hole where the rear O2 sensor is supposed to go? Other than a check engine light obviously.

 

Mine seemed to run fine without it.

https://www.s2ki.com/s2000/topic/636...ar-o2-removed/

 

Secondary O2 sensor doesn't do much, so you can skip it.

But if you like, you can get replacement sensors from Autozone or something like that.