my friend has a 96 firebird and the stereo lowers the volume on its own ive heard of this before but cant find an explanation online (didnt look to hard) and i know u guys prolly know what causes this and what is needed to fix it

 

I think some late model GMs have this. It's where if you get above a certain RPM, the volume increases to make up for a more noisy engine I guess. It lowers when you slow down. As for me, I have only had the stock radio installed for 20 minutes before I yanked it out & put a CD changer.

 

it may have the Speed Compensation Volume (SCV) which will automatically raise or lower the volume depending on speed. On my old radio, the setting was behind the volume ****.