Check your tyre pressure. They should be a minimum of 32psi. I prefer 36psi on the 16" rims.
If you want to put aftermarket or standard seats in, they must have side airbags because the stock CL9 comes with side airbags. If you put a non-side airbag seat into the Euro, then you are disabling safety equipment, which then makes your car not road-worthy.

