I'm going to be installing a pioneer avic-x910bt in my 06 silverado ( bose system). I purchased the metra gmos-04 adapter to interface the radio with the bose system. As I understand the bypass,you move the mute wire on the radio harness and then ground it and the parking brake lead to ground,correct ? My confusion is this,the metra adapter also has a mute wire from the truck side of the harness(onstar I suspect). So do I just cap that wire now and assume the mute will not work with onstar now,which isn't a big deal as I don't use onstar anyway. Or would a better option be to just install another wire in the empty pin spot for the bypass and use the mute wire on the radio as intended. Thanks for clearing up my confusion.

The mute wire is just like any other wire. So the answer is yes, any unused wire place in the slot as detailed in the bypass instructions will work.

Thanks for the clarification. Do you have any idea where I can get a pin to fit in the empty slot for the bypass or a p/n for it.

No, sorry. Someone on here said that most installers will have wires left over from alarm installations that will work. You might want to try your local shop.