I hope I am not too late to help someone, I just got gold in this today after a few frustrated attempts a few days ago. I had a few 1:35s and 1:36s, even a 1:38 on a mistake but had a 1:33.9 in the end! I overtook for P1 in the exit of the penultimate corner and I just coasted as I quickly got a 3s lead by the line.
-Add front splitter and rear wing. Wing set at 10.
-Stage 3 weight reduction and then added 14kg of ballast, all to the rear of the car.
-Turbo 2, ECU and other stuff. My car was around 500HP so I set the Power Limiter to 393HP (as after a couple of tries your engine breaks in and has more power).
-Your choice of 6-speed or fully customizable, set to top speed of about 260km/h (140mph)
-Fully adjustable LSD, don't change anything except for Differential at 35/65. Suspension with all default settings except for ride height (5,-15), rear spring 1 point less than front, so your rear is softer.
- Brakes as 2 and 6.
The key is to really brake well and not turn in too early, and be patient to only use the throttle when the car is properly lined up to exit the corner. I just went with that and won using just the DualShock 3 however I am unhappy that I again won a car I already own, grr!

I spent all that money on the Toyota GT-One... and I just recently exchanged 2 gift cards (1,000km, Lv23) for an old Integra and Jeff Gordon's Nascar. Soooo unhappy!
Edit: If anyone wants, add me on PSN and I'll make my cars available for each of the events as I had them set. I race on Manual gears with ABS set to 1, all rest off.