I have an ‘09 GMC Sierra w/Onstar and right now I have an PAC-OS4. The one thing I don't like about this is I lost my backup sensor low sound. When I back up the sensors starts to beep. When I get closer and I should stop the beep gets low sounding or deep. Since I installed the PAC I lost that low sound. I have had this for a few years and it has always gotten on my nervous. I was wondering if any GMC owners have installed the GMOS-100 and how good it works. I was told by a Metra tech that this retains the chimes and it sounds through the driver side door speaker. Is it worth making the change? How do the chimes and turn signals sound? Thanks for your help. (If anyone can post a video, it would be awesome! Thanks again.)