When it comes to your car's performance, it's essential to consider its Performance Potential. This crucial metric takes into account your vehicle's basic performance capabilities and any upgrades you've made from stage 1 to 9.

For example, the (+4) number in the image below is showing how much PP the upgrade you are viewing will award if you fit it. In this image the Stage 2 Transmission will raise PP by 4.

By keeping an eye on these numbers, you can gauge the effectiveness of your modifications and make adjustments accordingly.