The MetroStars, who had beaten the Galaxy 2-1 at Giants Stadium on Saturday, scored first in the 16th minute. Guevara, after a long series of passes, ripped a 25-yard shot past Galaxy keeper Kevin Hartman.
Gaven scored his first goal of the season after taking a Guevara pass to the left of the goal area, side-stepping Marcelo Saragosa, and hammering a close-range shot past Hartman.
Gaven's second goal was a perfectly curved left-footed shot from the top right edge of the penalty area that curled past diving Hartman's finger tips into the far post.
June 23 in Carson, Calif. LOS ANGELES 0 (6-5-3, 21 pts) METROSTARS 3 (5-3-4, 19 pts) Goals: Guevara (Clark) 16, Gaven (Guevara) 39, Gaven (Guevara) 43.
Los Angeles -- Hartman, Lewis (Victorine, 46), Califf, Suarez (Ngwenya, 66), Broome, Jones, Herzog, Saragosa, Grabavoy (Alejandro Moreno 72), Ruiz, Kirovski.
MetroStars -- Walker, Leitch, Parke, Pope, Regan, Gaven (Galvan Rey, 79), Clark, Guevara, Gilberto, Magee (Brenes 72), Wolyniec (Glen, 58).
Referee: Abiodun Okulaja Att.: 18,342.