the siver-red sports cars are Yakuza cars. *the Yardies drive cars that look like the Idaho and Esperanto, big Cadillac types. *they're all the same reddish brown color, with leopard print upholstery inside. *drive around the four lane highway just south of the construction site to find some. *the Yardies are the ones with the Rastafarian look and accent. *their cars are the only one that don't have a horn, instead they...hit the L3 button (push the left analog stick in) and you'll see.
when you get in the Yardie car it should say 'Yardie Lobo' onscreen for a moment.

once you get the correct car, your contact will appear on the radar. *pick him up and drive to the hospital parking lot. *you might want to face the car so the Cartel cars are on your right before you stop in the blue circle. *and some Molotov corktails will help.