In my "new to me" 200 Echo, 52K miles, 4D, manual, when I am at idle with the A/C on, I often hear this "wuh-wuh-wuh" sound from the dash area. A local mechanic, who is usually a very good diagnostition, explained that there was a vibration within the dash because the engine/transmission/etc. has an unusual amount of vibration. His first guess was bad engine mounts but, on inspection, the rear mounts are a little squashed, but not enough to explain the vibration. Something not visible is out of balance.
He suggests taking it to a dealer who has all the technical bulletins on that specific car. While waiting to set up that appointment, I though I'd ask if this sounded familiar to anyone here. Does it?