I'll second the recommendation to test the temp sensor. Also, if you want to see if the O2 sensor is causing a problem (fluctuating idle is one symptom of a bad O2 sensor), unplug it and see how it runs.
The "bogging down" is usually a mixture issue, so the temp sensor (or the wiring, including grounds) is the #1 suspect for that. The grounds for the F.I. are the black wires with ring terminal ends that attach to the cam cover. If these don't have a good ground the ECU doesn't work well, since one of them is the reference ground for the O2 sensor and temp sensor.
When all else is good, also make sure the idle is set correctly, no more than 1000rpm. Above that and you can get into a sort of high-low-idle feedback loop.