The Yans inflict the virus status which stops one character from getting exp. but that can be used to your advantage. When the exp. doesnt go to the inflicted character it goes to another charcter and that character can level up faster. On my best file for FF9 they are all level 99 and the time it took me was 93 hours and 37 minutes. No freaking joke. I know i need a life...The yans will counter with either snort or float. Their attacks are usually Meteor and Virus Powder. So here's what you can do: Wait in a battle until a yan casts virus powder on three of your characters. Then all the exp will go to one character, and he will get four or five level ups. Cast Death with Vivi and summon Odin with Garnet. When you are not using them have Steiner cast Shock and everyone else concentrate on killing one yan at a time. It could help to have auto life. I did that and it took me forever. But you cant find a better monster than the yans so start hunting.