Nah, it's 4 EV's added onto the 1 or 2 you already gained. So fighting a Gyarados with a Power Brace equipped would be 2 Attack EV's + 4 from the Brace. And then the Pokerus bonus is multiplied, meaning 6 x 2, equalling a whopping 12 EV's from one fight.
Man, Diamond and Pearl made it real easy to EV train.
(Work In Progress)</center>