There are 2 vent tubes coming from the valve cover, Because we all know we cant have oil fumes going out into our air, stupid emissions. So toyota runs it back into the intake and it basically allows oil to pour into your throttle body and gum up the butterfly and the rest of the intake plenum. I took mine off and scrubbed the crap out of it with degreaser. It was caked on thick inside mine. Makes the motor run a hell of a lot better when you get 15 years of oil build up out of it and get the butterfly really clean too. I took the front vent tube off and plugged it and put a k&n style vent filter on top of the valve cover to prevent the throttle body from getting gummed up again.
