Mine shakes as well, doing 120 I can feel the gas pedal, steering wheel, arm rest and seat all vibrating. Its not a massive shacking but just enough for me to worry about whats going to happen in the long run.
I went out side to look at my splash guards and the rear drivers side screws were coming off so I got my driver and started to screw them back in but to my amazement my rear bumper cover is as lose as hell.
The plastic rivets are all there its just really really loose. I can grab it and move it 3/16 either way around the rivets. I am going down to the dealership tomorrow to order some standard bling parts so I will ask them what they think.