Santana throttle has an air filter connected to a vacuum tube. What is this for?

The purpose of Santana throttle connecting air filter with air pipe is to filter the air needed for cylinder combustion, reduce dust entering the cylinder, reduce cylinder wear and improve engine life. In addition, the length of the intake pipe is estimated. In order to get the most suitable intake air with the same caliber, the resonance frequency of the pipeline should be the same as that of the cylinder as much as possible in the design to get the most suitable intake air. Some vehicles are equipped with engine ventilation pipes on the intake pipe, the main purpose of which is to recover the residual oil and gas leaked from the valve and carbon canister, and then inhale it into the engine for re-combustion to reduce air pollution.