Was driving my Sister's 2010 XC90 with 110k miles the other day. It drives fine but noticed that that when cruising along between 30mph to 60mph and I press the gas to accelerate there is a growling sound coming from the front. Can't tell whether its from engine or drive train. According to them its been that way since they got the car at around 30k miles. The dealer supposedly told them thats the characteristic of the 3.2. Any thoughts.