With 220 hp you need grip. There's a reason the SHO came with V rated rubber, Z rated in the later models. Kumho makes a great autocross tire but their street tires are average. Nittos are also an average tire. The Firestone SZ-50, Dunlop 8000, Bridgestone RE730, and Yokohama AVS are good sticky tires. You should get 15k-20k from them. The best thing to do is put some 4 for $100 tires on your SHO and go to your favorite curves, record your speed and handling feel of the car. Then put some of these Z rated tires on and do the same thing. Sticky rubber makes your car safer, the ABS will not kick in as soon, steering is sharper, and you can accelerate without wheelspin, etc.