HiI drove my 2005 B7 2.0 TDI (140 PD) from Southampton to Inverness today (do this route now and again) and after driving about 400 miles, the engine noise developed a constant hum, though performance was unaffected. Gave the car a 2 hr rest at Perth before continuing journey but again the engine noise returned. Completed journey but got no idea what's wrong...car's performance is normal ( no warning lights or anything) its just the noise which is abnormal....its a constant rumble and definitely coming from engine. Any idea what could be wrong? Engine is BLB and had balance shaft replaced and changed to gear driven by audi dealership last year as a precaution and also had my car remapped by Shark STS (diy jobbie). Will take off Shark map tomorrow but really worried my engine may have gone tits up... as car has only done 75k 
cheers
cheers
