If your main goal is to increase the sound of your Suzuki Gixxer SF, modifying the exhaust system is generally a more effective option compared to changing the air filter. The exhaust system plays a significant role in the sound produced by a motorcycle. By replacing the stock exhaust with an aftermarket exhaust or installing a slip-on muffler, you can often achieve a deeper and louder exhaust note.
It's important to note that modifying the exhaust system may have legal implications depending on the regulations in your jurisdiction. Some areas have restrictions on noise levels and modifications to the exhaust system. Before making any modifications, it's essential to research and understand the local laws and regulations to ensure compliance.
On the other hand, changing the air filter alone will not have a significant impact on the sound of your motorcycle. Air filters primarily affect the airflow to the engine and can have a minor impact on performance, but they are not primarily designed to alter the sound.
If you're considering modifications for sound purposes, it's recommended to consult with a reputable motorcycle mechanic or a knowledgeable expert who can provide guidance on the specific modifications that are compatible with your motorcycle model, legal requirements, and the desired sound outcome.