This thread has me wondering about something similar on my 4runner. I have a similar issue as in that after a drive, and restart while warm the truck will idle rather roughly, but drives just fine with no bogging or hesitation. When it's cold it idles smooth as silk. I just redid the exhuast with new cat, larger pipe and new muffler and that seems to have helped a little but its still there, not a major problem, just an annoyance.

As far as I can tell the O2 sensor is original with 192k on it. I don't have any codes and milage is not bad, but I wonder if my sensor could be getting tired? I hate to replace it if it's perfectly fine, but if it will make my idle smoother I'm all for it.