That is what I did to mine. The biggest improvement came from using paint on deadener such as Spraydead on the front wheel well section near the door. This is the part not covered with a liner. 4 coats and the engine noise was much less. I also did Raamat (similar to Dynamat but less expensive and just as good) on the rear hatch area including a lot in the spare tire hole, inside the rear hatch and somewhat up the sides. It did not make that much difference. http://www.spraydead.com/
Found this information on a UK web site review of the 2014:
To improve body rigidity, Lexus has broken out the structural adhesive and found space for 20 additional spot welds around the tailgate, allowing it to adjust the spring rates on the CT200h’s notoriously tough suspension. It has also introduced 94 separate measures to combat the car’s thoroughly un-Lexus like NVH problems, including improved sound deadening behind the dash and in the rear arches.