Hello dear E90 community, Looking for desperate without success, I have decided to describe my problems in this forum. Whenever I have the engine turned to about 1800 rpm, a rhythmic hissing sound is to be heard and stops at about 2400 rpm. I have a video on YouTube that has exactly the same problem as me, and in the comments of this video it says that it is the control chain or is a quite normal noise. However, since I know how to use the I’m not sure if it’s really the control chain. When I turn on my car in the morning, there’s no rattle or sound like that. I hope someone can clear me up or calm me down. Here’s a video on YouTube with the same sound as with me.https://youtube.com/shorts/91ShzAo6-0E?feature=share