To give you a helpful answer, I need some more information. Please tell me:
* What year is your Suzuki Forenza? This will help determine the model's specific parts.
* What is the box like? Describe its shape, size, material, or any markings you can see on it.
* Where exactly is it located on the throttle body? Is it connected to the throttle body, or mounted near it?
Once I have a better understanding of what you're asking about, I can help you identify the "box" and its function.