About tunning. Who make a tunning is good for himself. You dont have same style of driving. I see on this forum hundred of aberation. I ran online in Super GT 500 series. This cars have very good balance. Some people like understeering, some not. With stock car Nissan Yellowhat Tomica GTR 08, only oil change,R3 tires, just raise rear heigh (raise how is good for you) for online races you can do easy 6.20. on the "ring. Offline you have a huge amount of grip. Remember: With practice and practice you gain seconds of lap time. In the GTR Woodone you feel oversteering. In Calsonic, Xanavi, Yellowhat you feel understeering.
