ok what controls the shifts on a 1999 aode from a mustang, is it vacuum controlled, pressure controlled or what, mine is shifting very early?

1st to 2nd by 19 mph and into 3rd by 30 mph and od by 35 mph

tried several tunes and it is not from that. any ideas
i can make a left turn and be in third by the time i finish the turn and if i need to get on it it will kick down 2 gears to first

thanks

 

ok after looking up info i have determined 1st to 2nd is normal, its my 2-3 shift that is messed up

anyone know anything about these aode's