I drive a 2004 Audi A4B6 1.8t. Recently a weird sound has popped up.. I can't replicate the sound with the car stationary. When I drive at 2000rpm there is a strange rattling sound, nothing before and nothing after. It can be heard as you go up in all gears (at 2000rpm) and when you come down the rev range past 2000 again. I've uploaded a video here: The only thing I can think of is a vibrating heat shield. I have checked them all and they are all tight. Any ideas will be appreciated.