The Performance Shop is separated into five smaller subsections:
- Engine (Turbo, Supercharger, Intake, Headers, Exhaust, Computer, Jet Kits, Engine Upgrade, Nitrous)
- Transmission (Clutch, Gear Kits)
- Chassis (Suspension, Sway Bars, Airbags, Hydraulics)
All parts can be upgraded from stock to two levels, except for tires which can be upgraded from stock to three levels. Players can also select a brand for each part. Different brands have no effect on the performance of these parts. Brands are the same between levels 1 and 2 except for tires and brakes. Tire brands are chosen in the Body Shop while brakes have one set of brands at level 1 and only Brembo at level 2.
Part levels are unlocked during gameplay as the player completes races. At the start of the game, only level 1 for Class D cars are available. Any part levels that should be unlocked while in a particular city will be unlocked upon the defeat of the city champion if they haven't been unlocked by then.
Motorcycles (Choppers and Sport Bikes) have a different set of performance parts from four-wheeled vehicles. Only Jet Kits (which are not available to car and trucks), Exhaust, Engine Upgrade, and Nitrous upgrades are available.
Exotics, AMG vehicles, and the Gemballa GT 750 can only be upgraded with Nitrous and, in some cases, airbags. Also, Classic/Muscle cars (aside from the '96 Chevrolet Impala SS) do not have the Computer option available. Additionally, vehicles that can be upgraded with Turbo cannot be upgraded with a Supercharger and vice versa.