yellowbastard in the basement has a really nice 350Z, try to shoot him a PM.

Changing your tire size is going to throw off your speedo. Either upgrade to 18/19 or try to keep it the same. Nissan engineers fitted the correct size tires to your car to begin with, so changing it will affect handling and ride and not in the positive way. Didn't the track model come with different sized wheels/tires? You might wanna try that combo.