Well then there you have it. If the problem travels with the TB, then you have your culprit.
That's why I bought a new throttle from Toyota.
But after installed the new throttle, the car has similar behaviour but in better way:
1. The idle will drop from whatever to 1200-1500 quick as normal. Then slowly drop to 900-1000. But at around 1100, I can see the A/F meter go up from 14.X to 13.X then back to 14.7. With that 13.X the idle will goes up a little then back down to normal.
2. If the car is not rolling, the idle will drop to 900-1000 slowly, and act the same as above (But at around 1100, I can see the A/F meter go up from 14.X to 13.X then back to 14.7. With that 13.X the idle will goes up a little then back down to normal).
3. If the car is rolling (no clutch, no gas padel), the idle will not drop below 1100. Just continue hold at around 1100.
4. If the car is roll to stop at red night with no clutch, the idle will drop slowly without that bump.
5. In first gear without gas, release the clutch slowly, the car will roll by itself and maintain at around 1100, no stall, keep on going by itself. I can see the A/F meter will go up to 8.X to maintain not to stall and back to 16.X, then cycle again. The car roll quite smoothly, LOL.
6. Same as in second gear.