JVB heres how to do it:
drive slowly, if he's out of sight he'll get stuck on a bridge, bug ingame.
trick:
get a sniperrifle, go to malibu to get the quest, then when you get outside, and the two cars are in front of you use the sniper to headshot the driver of the other car. The mission will fail, but you'll have his car. park it in a garage, to save it.
