1998 xk8 replacement shocks and springs.
I replaced my shocks and springs last year and the car now rides very hard. They are quality parts but not xk8 original. Would this make a difference?

 

If they weren't specifically engineered for an X100 model Jag they could most definitely be too hard/stiff for your car. Also did they have any adjustability to them as some higher end shocks (Koni for instance) do have various settings you can make even after installation.