[DWR]

Originally Posted by Lexx.md

The idea of having them mostly is to be able to change length of intake, sometimes it is better ti have longer tubes, sometime shorter.
Probably on full load they are open to get as much air as possible.

They are called swirl flaps because they block one of the 2 intake ports and that causes the airflow to swirl as it enters the combustion chamber. The injection pressures are much lower at low load/rpm, so the swirl action helps the mixing of fuel and air.