Carlyle Mitchell had the only goal for Vancouver (6-4-7), whichplayed a man down after defender Jordan Harvey was shown a red card for a two-footed challenge in the 69th minute.
Torres headed home a cross from Marky Delgado past a helpless David Ousted. Torres, who has scored in five straight games, now has 13 goals on the season for a Chivas team that has scored just 19 times.
Mitchell headed home Pedro Morales' corner in the 27th minute for the Whitecaps, but Pelletieri replied for Chivas in the 47th to tie the score.
Barrera capped the scoring on the last kick of the game after the Whitecaps sent Ousted forward on a corner kick.