I just got my 2006 GT 2 weeks ago, the stereo worked fine the first week, but on this last monday it's been having issues. It has the shaker 500 system, and when I start the car it works, but after a few minutes it will act as if someone turned the volume down. If I turn the volume up more, I will get some sound but you can tell there is no bass. The bass will come back occasionally but will usually just fade away again moments later. I can't leave the volume up higher as when the bass comes back it's suddenly way to loud. I've done google searches and get very little info, in fact I really only found two other threads regarding this specific issue. One of them blames the head unit and the other blames the amps. Neither issue is concluded so I don't know if either of them works. I do plan on getting another head unit eventually, hopefully if tax time isn't to brutal but would like to know if that will fix the issue.