During any race, achieve a time that makes the top ten list of scores for that level. Now, scroll down to the bottom of the screen, and hold the control stick to the left for about thirty seconds. A person's head will roll on the conveyor belt when done correctly. Now, select a car that is fully powered-up and begin a race. Every checkpoint you travel through earns you one Nitro boost. To use this boost, press brake, brake, brake, gas, brake, and gas.