Being I had no service history and suspected no such work was done on my 500Sl, like Loren I just had my chain replaced as a precaution, at 100K. I also had the three chain guides, chain tensioner, valve stem seals and cam oiler kits replaced while they were in there. The engine runs smooth and very quiet now. Not cheap, $1,900.00, but now I drive it confidently where before I was always a little uneasy about not being sure if the chain was good or not. I too had a slight rattle sound a startup.