The trick is, dont get a nudge from the other cars!
I did this last night in the 787b stealth unmodified, the first time i'd driven the car. Max downforce, a little tuning for each circuit (Softer suspension and raised for the ring with toe in for stability etc)
Came first in every race. Spent 2/3 laps "pacing out" the lead car to see what kind of speed he was doing everywhere. After that i passed him, got myself a 1-2 second lead then put it into "bring it home mode"
The trick with these cars is to be very smooth and very sensitive inputs. Only go full throttle or full brakes in a straight line really.
P.s i apologise if i appear all "its really easy!" about this and the 787b is actualy insanely fast.