M110 DJet 280E air setting

HelloMy car is 1976 W114 280E djetronic.The carbon setting is 2% at the level of 2.5%. However, I hear a loud air suction sound from the air intake bellows. When we watch in the attached video, a high amount of air suction sound comes from the air bellows. Is this normal?  Or should I lower the idle so that there is no air intake noise?thanks for answers.

Hi,

I am not sure I can follow you. But there should not be a hissing sound.

Thanks