I have this exact same problem on my '86 non-turbo. The only thing I've noticed other then what you have pointed out is that the sound is not actully coming from the back right side of the car. It is bouncing off of there, but is actully coming from a small fan next to the lights on the strip between the t-tops. Mine only buzzes when my car isn't going to start as well, but I can't figure out the connection that is has with the problem. Mine has failed to start cold, but seems to have more problems when it is warm. In fact it is basically undrivable in the summer. You're the only other person I've found with this problem so maybe between the two of us we can figure something out eh?