On engines with variable valve gear, no vacuum is created in the intake system in unthrottled operation.
However, for certain functions, a vacuum is necessary, e.g. tank ventilation, brake booster, possibly also exhaust gas recirculation.
This required vacuum must now be generated by a special function of the engine control. To achieve this, the electrical throttle-valve actuator is closed until the intake pipe pressure sensor indicates the desired vacuum.
This is why the intake pipe pressure sensor is fitted after the throttle valve in the intake system.
However, the vacuums created here are very much less than those that occur on engines without variable valve gear in certain operating states.