Atm,
After reading and responding to your initial post and reading much of this thread, I was curious. So the next time I was out in my X-trail, I shut down the AC, fan and stereo and let it idle in Drive (about 750 RPM according to the tach). My observations: No vibration at all through the seat, floor, firewall, shifter or console. None in the steering wheel if you grip it normally, but there is a hint of vibration if you let go of the wheel and just contact it lightly with your fingertips. As for noise, it's about as quiet at idle as the best of the 20+ vehicles I've owned. The only unusual noise is a very soft murmur which I believe is the power-steering pump. Maybe that's what you've been trying to describe??