When I picked up my 335i sport it had 18" run-flats. I thought the ride was pretty stiff. I switched to 19" non run-flats and the ride improved, much better. Tire geometry will affect the ride as will tread design.
By any chance do you have the seat in a new position? I find that I am very sensitive to seating position. Has something to do with the 16 screws, 4 rods, 3 shims and butterfly plate I have in my spine.
That said, I find the sport package comfortable.
Alan