What is the most effective way to increase the horsepower of my Audi A4?

I'm looking for ways to boost the performance of my Audi A4. What modifications or enhancements can I make to increase its horsepower? I'm open to both DIY options and professional services.

One of the most effective ways to increase the horsepower of your Audi A4 is by installing a performance chip. This will optimize your engine's fuel and air mixture, resulting in an increase in horsepower and torque. I've personally had great results with the "RaceChip" brand. Also, remember to regularly tune-up your engine to maintain its performance.