I have not long taken delivery of a 2005 Volkswagen Golf TDI 4-motion with 67,000 miles that also has a most awful droning noise at approximately 2000rpm or 68-70 mph. It's as if the vehicle shouldn't be in the highest gear: sixth, but a lower one. I get the feeling that it's coming from the rear of my car but could easily be the exhaust, but not the tyres which are brand new Michelin Alpin3. Luckily I haven't had to drive for too long a journey yet but am not looking forwards to it when it comes.