The first thing a person should upgrade if he wants more performance out of his car is the tires. Think about it. If you have the world's best engine, the world's best suspension, the world's best chassis, the world's best brakes, and some cart wheels from an Amish buggy, your car will suck. The tires are the only part of the car that actually interfaces with the road. Good tires are what really make a good car.