Open your bonnet when your rpm is at 600, you can see your whole engines is vibrating and any parts linking back to your body which caused this vibration.
So far my car was the air intake compartment that cause the problem, after tcm placed "cushioning", no vibration.
It linked back to your petrol used. 95 and 98 will make the difference. Good tuning can also solve the vibration even if you use 92 and 95. Sensitive drivers will feel the different petrol use and you step on your accerator.