I've got a great tune of the car, but I don't know how much it will serve you if you are using it over 621hp... I can't access it now, but I'll shoot it to you ASAP.
EDIT: Here it is, I hope you enjoy.
Downforce: 65/80
Weight: 900kg
Power: 531hp-621hp
Turbo kit: Stage 2 (allows for monster torque out of this monster car)