I've got a 2003 B6 S4 and I've just had a new sub frame fitted, the old one was dangerously rusted. A mechanic friend did the work and when he was away when I picked the car up. Driving it back, I immediately noticed a few new noises.

Firstly and most noticeable while driving a is a sort of windy whine that increases with the revs. Most noticeable between about 800 - 2000rpm, after that the engine and exhaust starts to drown it out. It's a bit whiny and possibly a heavy rush of air, although it's a bit hard to describe. Kind of a cross between a supercharger, jet engine and a turbo diesel whine!

On top of this the car feel like it's idling a tiny but faster than before, plus when I dip the clutch to change gear, the revs hold for a split second before dropping, possibly even increase a fraction before dropping. This is all new.

Second thing is I've noticed a slight whine when I turn the wheel when I'm stationary or manoeuvring very slowly, almost turns to a squeal on full lock. I'm guessing possibly something to do with the power steering?

Finally there some vibration I can notice at low revs, I'm assuming this might be something to do with the sub frame or the fitting.

Any thoughts on the first issue or where to start investigating? I love to car, but I'm getting to the end of my tether with it at the moment.