[The Radium King]

sorry, i confused the two. a venturi in this context is usually associated with vacuum. this looks like a bypass around the throttlebody at idle, using an existing port on the manifold (the manifolds are the same piece reversed, so the brake booster port is available). at idle air is drawn from the intake tube into the manifold (throttlebody is closed and there is a vacuum in the manifold as a result). it moves past the y fitting and creates a vacuum. where does the third end of the venturi system connect to? probably to do with idle control and the torque converter, or maybe just to create additional vacuum for additional functions.