Over-Revving
You will find with some of the Cars when launching that over-revving and timing it so the needle falls back into the correct zone at the end of the countdown will give you the best start.
Wheelspin
You can help avoid wheelspin when you start or shift by either shifting a bit earlier or launching at a slightly lower RPM.
Tuning
Look to increase the performance of your car by tuning it. Whenever you adjust your nitrous, tires, or any other part of the car, you will see the +nn change indicating the overall potential decrease or increase. Retune your car whenever you get new upgrades.
Level Up
Make sure that you level up your nitrous, transmission and tires whenever you are able to so you increase the performance of your car.
Perks
Joining a Crew is a good way to get perks for your car.
Beat Tyler Shax
The video below will show you how you can beat the tier 5 boss Tyler Shax with a fully upgraded tier 5 car, in this case a Lamborghini Huracan 707hp has been used.