I had the same idle symptoms as you, and searched, searched, searched every forum. I'm telling you I did everything (IAVC, FITV, adjustment, timing, even replaced the O2).

Finally fixed it by filling up a squirt bottle with water, and started spraying stuff. Turned out to be the TB gasket. Then it made perfect sense. Before the engine warms up the butterfly in the TB is partially open, after the engine warms up it almost closes, and the IAVC controls how much air bypasses the butterfly, and starts controling idle. Once the butterfly closed the engine started pulling air in at the TB gasket. Then the IACV would try to compensate, over and over causing the fluctuation. I bet you have a leak either at the TB, or IM.