The car is so well as it is that there isn't much tuning you can do to benefit it. Add the aftermarket turbocharger if you have to, and I like to maximize downforce, even out the spring rates and reduce rear toe angle to 0.10. Lower the transmission to 155 or 162 so that you can come out of corners faster. If you're having problems with the oversteer be easier on the throttle when coming out of corners. Also be sure to turn off all driving aids, except ABS 1.