Mine was built in Nov of '09. Very quiet as well Had to get the exhaust changed out just to hear it. However the vibration is there in mine.
I can feel it in the gas pedal and in the steering wheel. at approx 35 to 50mph. Then it goes away. It does while coasting, around corners, uphill, downhill, etc. The vibration does not change with speed. Stays constant until you go past around 50. I have tried to make it change harmonics by cutting the wheel real hard around a pretty sharp turn, by my house. Vibration kind of goes away but still there.