The link I gave was this one
http://guidesarchive.ign.com/guides/504/rankings.html thats also the one I looked at, not this other one you are now talking about. The one I am linking is from the IGN guide, that makes it pretty certain to be true. It quite clearly says that to get the best rank you CAN NOT save at all. MUST beat a certain time and not use First Aid sprays. No mention of herbs, but I would say none of them either. And only using stuff liike the Pistol and Shotgun.
I am not saying that this will get you the S rank, as the website says it will get you the A rank. Which according to them is the highest rank, now that I think about I never saw what rank my uncle got just that he got the best one. It is in fact possible that there is no S rank. The manual could be wrong, or miss translated.
So try again see what happens, you are already doing an awesome job beating the game in the hardest way possible.