Keeping in mind that most road-going cars are built to be as economic and reliable as possible, performing any of these following upgrades can subsequently change how the car behaves and feels. Be sure to document yourself thoroughly before investing time and money into anything.
1. Intake and Exhaust
On a stock motor, overall results from a CAI (cold-air-intake) and catbacks (performance exhaust systems) are more “show” than “go”. That said, engine/exhaust noise is more noticeable and a minimal increase in horsepower (if done correctly) is also possible. A cleaner-looking engine bay and a chromed dual-exhaust is always a good start, too.
2. Reprogrammed ECU (Electronic Control Unit)
To avoid flashing “check engine” lights and mechanical maladies (such as a rough engine start/idle) a performance-tuned ECU is highly encouraged, as it will better “understand” any significant changes in horsepower/torque data. In automatic transmissions, an ECU can also be used to modify gear ratios (so the transmission will shift faster).
3. Turbocharger/Supercharger upgrades
Turbo and supercharger kits are often extremely expensive, but they can equally provide the oomph that you want (with the rule of thumb being that you ensure your engine can safely withstand such major upgrades.) If mechanically-savvy, do-it-yourself kits can save you hundreds of dollars in installation costs, otherwise, it’s best to have a professional do it for you.
Standard drivers can get “short-shift” kits which reduce the time between changing gears, and can increase acceleration. Performance clutch upgrades can also help the transmission cope better with higher engine torque/horsepower.
A good set of rims and tires can be more than just attractive swag, as they can make all the difference in your car’s overall responsiveness. Though stock rims are more resistant to corrosion and wear, some aftermarket rims are lighter and wider, accommodating more rubber and increasing overall grip on the road.