What are the best performance parts for an Audi S4?

I recently bought an Audi S4 and I want to upgrade its performance. I have some basic understanding of cars but not too technical. Which specific performance parts should I consider and what kind of improvement can I expect?

I recommend starting with an ECU tune to gain more horsepower and torque while maintaining reliability. Pair it with an upgraded air intake system for even better performance.

You can also upgrade the exhaust system to improve the sound and add some power. Just make sure to choose a quality brand to avoid any potential issues.

If you're looking for more significant gains, consider upgrading the turbochargers and intercooler. This will require more technical knowledge and may also affect the car's reliability.