The way the speakers are wired is beyond belief. Do you lose all sound or just from one speaker at at a time?
BTW - i'm getting my Bose system upgraded (it's truly rubbish - those placing orders save your money. I'll post photos of the speakers when i get my car back and you'll wonder where your money went) and the guys at Audio Advice are having no end of problems with doing the upgrade.The positioning of one of the amps ridiculous too.
I went to visit Audio Advice on Saturday and saw my car in bits, and saw all the bits, and it's a joke of an audio install. They said they have never worked with anything like it in all their years. As great as the car is, the Bose sound system is poor. I've asked them to do a write up as they are now by far and away one of (if not the) most experienced car audio installers when it comes to the GTR. I'll post it here too when it's done.