What does Passat intake manifold check valve do?

The function is that when the engine speed reaches more than 3000 rpm, the solenoid valve of the thin tube is opened, and the vacuum suction will suck up this part of the vacuum valve, and the rod on the vacuum valve will pull up the steam trap and turn it into a short tube, which will increase the torque.

For carburetor or throttle body gasoline injection engine, intake manifold refers to the intake pipe from the back of carburetor or throttle body to the front of cylinder head intake. Its function is to distribute the mixture from carburetor or throttle body to the air intake of each cylinder. For port fuel injection engines or diesel engines, the intake manifold only distributes clean air to the intake of each cylinder. The intake manifold must distribute air, fuel mixture or clean air to each cylinder as evenly as possible, so the length of air flow channels in the intake manifold should be as equal as possible. In order to reduce airflow resistance and improve intake capacity, the inner wall of intake manifold should be smooth.