André, any engine will perform its best when everything is as close to spec as possible, and while you have it apart, you might as well do it right. I check spring heights, tension, set them on a straight edge and check them for being square. I also check the valve spring height. I would buy new springs and check them. Not all new springs are correct. I would also check the valves. The stem tips have to be ground to compensate for seat and face grinding. I know that there are machine shops in Germany that are very competent in doing this. I visit Germany quite often and have seen some of the machine shops. In fact, I will be in Germany later this week.
