You can't tell the condition of an O2 by a visual inspection, unless it's obviously broken. I apologize if you've mentioned this already, but have you gotten an O2 sensor code? If not, they are more than likely fine. As per the other thread, I highly doubt the injectors are the problem.
In my experience, a lot of idle over heating conditions are simply due to an old A/C condenser blocking air flow. Road debris will smash up the fins which substantially blocks air flow. At speed it isn't an issue because of the additional air pressure in front of the cores, but just sitting there any small blockage can cause a substantial decrease in flow. I've fixed two cars idle overheating problems by simply pulling or replacing the condenser. Do you have a picture of your core and the fans you've added?
I would also definitely check the cats out as well if you haven't already done so. If you can get them red hot simply by holding the throttle open for less than 30 seconds, you may have an issue.