How long till the noise stops, you stopped videoing before it stopped?
First thing I would try is disconnect the wires to the Aux. Air pump. The engine runs absolutely fine without it and it runs on a timed circuit and will stop soon after start up. If you disconnect the wires and the noise doesn't start you have found it. Another thing I had on my Z3 was the idler pulley bearings on the Aux.drive belt.
Tony.