Slotted brakes does the job of removing gasses, while not reducing braking surface area. They can also better withstand warpage than cross drilled rotors. These upgrades allows you to more efficiently apply the power to the ground. Notice that I've made a well rounded car at this stage. I worked on the power AND handling of the car.
Engine performance increases due to the increase airflow and reduced pumping losses.
Handling will vastly improve over stock due to the superior tires and lighter wheels. This stage concentrates on handling. Camber plates will save your expensive tires from wearing out prematurely on the inside while still allowing you to adjust for maximum handling on the track. The upgraded ignition system is necessary when the spark requirements increase due to increased airflow. With all the horsepower that you have, you'll need the ability to come to a stop quickly and fade free.