I have a 2004 VW Lupo 1.4 - there's a vibration noise coming from the right side of the dash (inside the dash though, not the dash itself) when the engine hits 2500 - 3000 revs - the car has air con, could it be an air con system problem - the noise doesn't seem to be coming from the engine at all.
Hard to say, blower motor is on that side and they csn make growling or screeching noises when going bad. Oa an ac line or power steering line may need to be insulated from the body. Look for signs of hoses rubbing. Also try leaving the heat/ac off and test drive it. The switch it on while driving.