IV and EV data are stored in the AMP data for that monster (AMP = Active Monster Party, the monster individuals that are in your / the enemy's party, contrasted to the general notion of each species). So, held for each mon.
They work a bit differently in this engine, both to make them legally distinct and make monster stats grow faster so you don't need to grind levels to beat the demo. If you wanna make them more Pokémon-like, all the stat calculations are in the stat-computing scripts we talked about a couple days ago - just change them there and it will affect all the monster stats in the game.