[emil111]

yes hello i am writing this topic in order to help any other bmw owner that might hear a rattling knocking noise from under the seats and cannot locate it.

You need a tool that is long as thin as the one shown in the photos and poke it inside the airvents (you will need to be quite flexible) and if you come across an item that appears to be very long fear not! the 3 exit holes are connected and you can get any item that is stuck in the airvent out.(in my case a SCREWDRIVER).

This is worth checking if you have a knocking/bashing sound when you take corners at speeds over 20-30 kph (i only drive in town or on the motorway-so i dont take hard turns at high speeds very often)

[No one]

I never knew there were vents under the seats! I guess I do recognize the screwdriver though: it's an onboard tool, whose dedicated place (a hole to poke into) is in the front of the boot's left side storage compartment (that lockable flap), next to the towing eye. I reckon I could use the screwdriver to mount the number plates, but I didn't know it was there then: it's hard to notice and not mentioned in the manual.