What is the primary purpose of the intake manifold?

The intake manifold's primary purpose is to distribute the air-fuel mixture to the engine's cylinders. This is crucial because the engine needs a balanced and even supply of the mixture to ensure optimal combustion in each cylinder, which directly affects performance, efficiency, and emissions.

The design of the intake manifold is significant as it influences how well the engine breathes. It should promote smooth airflow and prevent turbulence, allowing each cylinder to receive the right amount of air-fuel mixture at the right time. Proper distribution helps to maintain engine balance and improves acceleration and throttle response.

The other options relate to different functions that are not primarily the responsibility of the intake manifold. For instance, filtering incoming air is part of the air intake system, typically involving an air filter that prevents contaminants from entering the engine. Storing excess fuel is not a function of the intake manifold; fuel is delivered by the fuel system, and while there may be some fuel rail storage, this is separate from the manifold's role. Finally, equalizing pressure in the fuel system is related to fuel pressure regulation, which does not fall under the manifold's primary duties.