I had the same problem with the big sweeper at the track i drove. My chassis was understeering at high speeds. I changed the setup and can now go full throttle through the sweeper. Besides the fact that my rollout was too high wich now i will reduce drasticly, that 0.5 seconds i had on the turbo was there cause i couldn't make that turn and had to go off the throttle. I thought with the 0.5 seconds i could make up for the fact that i had to go off the throttle. The motor only gets hotter then because it doesnt rev enough when the turbo kicks in. Reducing rollout and change the setup of the car is the ticket. That is my experience from last saterday anyway...