You have to be careful when describing vibration issues as I have not driven a singl;e 4 cylinder that I couldn't feel "slight" vibration through wheel. This is totally normalwith a auto at idle. when in neutral or slightly above it should disapate to nothing.
Also a passanger shouldn't really feel this without touching wheel, stick or other part of frame.
in general small 4 cylinder (under 2L) are smoother on avg cause of less mass and small stoke, this is were engines like honda 2.4L and may others use balance shafts to smooth out these large 4 cylinders.
You really should only feel slight vibration in wheel, brake pedal, the frame should be pretty smooth. It sounds like your just not familiar with 4 cylinders.
