Common performance upgrades for the Toyota Celica coupe include modified air intake and exhaust systems, lowering springs, Engine Control Unit tuning programs and forced-induction systems such as turbochargers and superchargers. Body kits are also popular modifications for the Celica. While some aftermarket body kits are only cosmetic in nature, other body modifications focus on improving the car's aerodynamics and grip at high speeds over stock models.
One of the easiest ways to improve the performance of a Toyota Celica is through the use of an Engine Control Unit software upgrade. Many professional tuners produce software upgrades that adjust the behavior of the vehicle's ECU to allow the engine to produce additional horsepower. These upgrades are relatively easy to perform and require no mechanical modification to the vehicle, though they may not be legal in some jurisdictions due to pollution control concerns. An ECU upgrade can yield up to 50 more peak horsepower over a stock engine.
Upgrades to the intake and exhaust systems of the Toyota Celica are another way to improve engine performance. Free-flow intake and exhaust systems improve the amount of oxygen available to the engine by bringing more air into the engine or by improving the clearance of exhaust gases. Forced-induction systems are more complex ways to improve engine airflow and power by compressing air with a turbocharger or supercharger and can achieve some of the highest horsepower gains of all engine modifications.