Hi again - back after a few months happy S4 ownership. There is however an intermittent noise at idle from the engine that doesn't sound right. I'm going to say it's something like a belt, pulley, turbo or flywheel. It is heard best through either wheelarch and sounds like a chirping noise over and above the typical diesel noise. It wasn't there when I first got the car. Have a listen to the 8 second video - the Audi technician says it's normal.