i was trying that one with TC & ASM off (as always) and i managed doing it Silver after a not so quick round.. but it was a pain in the butt.. i hate the sensibility for the disqualification, specialy when AI cars bump into you..
be sure you draft the last car at the beginning of the race, then overtake right and brake very late, i lift my foot from the gas before the corner (there is a GT sign above), then i brake shortly and after the car stabilize again i go second gear and i'm able to overtake the silver one already..
then you hunt that orange muscle car, don't go to quick, be sure you don't hear tire squeezing, means your to fast.. i then overtake all cars including the red one on the 2. gear right corner, you're allowed to go over the concrete corners too.
i'm not sure if i'm going to try it again even i could do it.. but i get very angry when i get disqualified unfair and that's just not worth it ;-)
good look