So when you are driving around it falls on its face and has no power with an idle issue?
First did you fix your plenum leak? If not replace your spark plugs and save to fix the plenum.
How did your fuel pressure test go?
Lets start with the easy and cheap thing first? When is the last time you did plugs, cap, rotor, wires? At least check them if its been a while, cap and rotors can corrode pretty fast given the right conditions.
Which O2 sensor are giving you a code, the upstream, or downstream? If its the upstream replace it and fix any pre O2 sensor exhaust leaks. If its downstream its only there to monitor Cat efficiency and wont effect anything.
Go to the parts store and have them load test the alternator, incorrect voltages can really screw with these systems sometimes.
Does your cat rattle or make noise, how long did you drive with a leaking plenum?
I had a Jeep that had a crack in the exhaust manifold pre-upstream O2 and it dumped massive amounts of fuel into the system because of the false reading. It overheated the cat which melted and started to rattle and plug up the exhaust, it would not idle for **** and had driving issues. New header, O2, cat, muffler and it drives like a new Jeep.