An o2 code is not going to make it idle like you are describing.
It sounds like the fitv is leaking... take your intake off and put your thumb on the fitv port on the bottom of the throttle body when the car is idling.

If this is not the issue then you have a vacuum leak elsewhere.

Code 23 will also not make the car idle nuts.

You can disable the o2 and code 23 for knock by having your ecu chipped.