Ever wonder what that vacuum actuated thing is at the side of a Toyota 1MZ/3MZ air intake is?
It controls a flap inside, to either disturb/redirect airflow for better mixing and reduction in intake valve noise, or to allow a direct unrestricted path at higher RPM's.
Here's a look at that flap:
Inside the intake plenum where it sits (note all the carbon buildup, especially around the PCV on the bottom:
The flaps don't end there. There's another one in this dual throttle body ES300 intake between the two throttle bodies:
Lesson learned while taking this apart: make sure you clean your car's air intake system, it can get really gummed up!