Honda Binzhi has a valve on the intake manifold. What is the gray pipe connected to the valve?

An intake manifold and an exhaust manifold.

The intake manifold is located between the throttle valve and the intake valve of the engine, so it is called a manifold, because after the air enters the throttle valve and passes through the manifold buffer system, the airflow channel branches here, corresponding to the number of cylinders of the engine. For example, there are four four four-cylinder engines and five five five-cylinder engines, which respectively introduce air into each cylinder. For port fuel injection engines or diesel engines, the intake manifold only distributes clean air to the intake of each cylinder.

The function of intake manifold is to distribute the combustible mixture supplied by carburetor to each cylinder. The function of the exhaust manifold is to collect the exhaust gas discharged from each cylinder, send it to the exhaust pipe and muffler, and then discharge it into the atmosphere.