Can't adjust volume of Siri while on Bluetooth

I just purchased the Belkin "CarAudio Connect AUX with Bluetooth" as a means to stream music and have simple playback/Siri controls in my car. This product is exactly what I was looking for. The audio streaming quality is very good. However, when using Siri, it is extremely loud and distorted and there is no way to adjust the volume.

I have researched this issue on many other forums and reviews only to find that it seems to be an issue with iOS. I am aware that you can adjust Siri's volume separately from the music playback volume, but when connected to a Bluetooth device, this feature seems to be disabled.

Has anyone else experienced this issue, and can we expect a fix in iOS 6.1?