There is very little legal ground here for any case against Nissan. This car is designed for street use. The car performs as such. If there's a heating issue while street driving, Nissan installed the limp mode to protect the engine. If you somehow destroy the engine prematurely during the warranty period during street use, Nissan will replace the engine. If you decide to add an aftermarket product to your car, if that screws up the car, Nissan won't honor the warranty.
The way to proceed here would be to make it a purely
PR issue. Raise a fuss. Make a stink. Call up all the car magazines and television shows. If it gets published in all magazines that the 370Z sucks on the track because it goes into limp mode after 1 lap around a track, people will stop buying it and Nissan will have to address the issue.