Most of us here in North America never saw S8’s. We got S6’s only. Over those three model years we did see, there were improvements. Off-hand things like strengthened 5th gear synchros, some additional bracing on the rear crossmember, strengthened clutch fork, and more durable interior finishes come to mind. Later series had better airflow to the radiator from the redesigned front bumper, elimination of a trouble-prone rubber coupler at the Y pipe outlet, improved turbos, a more powerful ECU and a better design for the solenoid rack. Probably more that I can’t remember. With the availability of parts that generally bolt-up to our older cars, many of us have incorporated a lot these improvements in our old, but LHD, S6’s.