Mine occasionally sticks at high idle. Some possible causes from my troubleshooting (at least things that definitely affect my idle).
Sticky throttle cable
Misadjusted or faulty throttle position sensor
Sticky or dirty throttle body
Vaccum leak
High or low fuel pressure (fuel pump pressure, fuel pressure regulator)
Various engine sensors (coolant temp for example has a big effect on how my 22R-E runs)
Cold start injector leaking (if the 5VZ has one, not sure)
Ignition timing, spark plugs, etc.
Did it come on suddenly? Since blipping the gas pedal quiets it, I'd at least start with the easy stuff. Throttle cable, cleaning the throttle body (inside, too, the 22R-E has a PCV return line into the TB that makes it nasty inside from that fuel & oil goop), checking for vaccum and intake leaks.
If you have a genuine factory service manual, they have nice flow charts to follow during diagnosis. If you don't have a FSM, TTORA has many of them online:
http://www.ncttora.com/fsm/