I did checked the tire pressure at dealership. All of them are 42psi. So, I released some air and made the front tires at 38 psi and rear at 37 psi (now, it is very cold in Chicago).
I keep with the specs (33/32 psi) and feel comfortable. But I also had 1 time 3 people on the back seats and a lady complained she felt a little bit sick (I was driving slower than usually in this case).For smaller bumps tires make a huge difference. Firstly, for FXT the psi should be much lower, IIRC 33/32.
To dampen small bumps even more change tires and/or switch to 17" wheels.