the title pretty much explains it all, how do i do this, so when i reflash a customers vehicle (LB7 or LLY) it says some thing different?

Should be in th user configuration folder of efilive.
Documents>EFI Live>V7.5>User Configuration>Messages.
I believe you have to make sure you keep the same amount of characters, no more or no less

you can have more or less characters, i think the max is 22 or something close to that. and i think this only works on the lly's but i could be wrong