Problems with vacuum booster

I think so, too. When the engine is idling, the throttle opening is very small, and the intake branch pipe is negative pressure, which provides vacuum for the vacuum pump. When the engine accelerates, the throttle valve opens and the pressure of the intake branch pipe rises, but negative pressure is formed in front of the throttle valve, because there is an air filter in front of the thick pipe, which instantly blocks the air passage and forms negative pressure in the thick pipe. This section of AB should have a conical structure, which will play a role when the AB tube converts vacuum. This structure is usually not used for middle and high-grade cars, but is replaced by electric vacuum pump. When the sensor detects that the pressure in the vacuum pump rises to a certain value, it will automatically start to provide negative pressure for the vacuum pump!

I hope my answer can help you!