I had a annoying fluttering noise coming from the engine somewhere for months and trying to find where it was coming from took a long time to find , it only happened from 1600 rpm to 2000 rpm and after 2000 rpm the noise would disappear at first I thought it was something to do with the Turbo which I found out it wasn’t I then thought it was a problem with the AC compressor I later found out it wasn’t that either so I wanted to tell people who might be experiencing the same noise because I did look everywhere to try and find information on anyone else who had this annoying noise coming from there car which I could only hear when the windows were down and going past parked cars and the noise would bounce off so to cut a long story short I found out it was the COD system ( cylinder on demand system) so I took my car to a tuning specialist who deactivated it from the ECU and now the annoying noise has completely gone , I’m so happy , I hope this helps anyone who is experiencing this who has the COD engine like mine which they fitted in Audi , Volkswagen , Seat, Skoda cars . 

Glad you got sorted 🙂