Final Fantasy IX max stats

Ive just started playing this game again but when i played it last time a mate of mine helped me max out all the stats but he neva told me how to do it but basically i wasnt able to change any items on people or it would wipe whatever he done and all my HP, MP, etc would drop right down.

any ideas what he did???

Thank You

My characters are all Level 99, so unless you want to cheat then its impossible, a fully levelled party with Auto-Regen is practially invincible anyway

I must admitt, i did try using a cheat device just to see what it was like, I have found a character that is more powerful than any other boss in the game! Stiener!! lol. I used every single Eidolon that garnet had at the time, and a couple of overpowered Blk magic skills.....and he still would not die!! lol. Made me giggle, only found out recently you can just do nothing in that battle and it automatically ends 0_o