I have a 1991 Audi V8 Quattro - great car with an overly complicated Bose audio system, the one with the amplified speakers that always squeal. Does anyone know what the major components are and where they're located, beyond the obvious ?? Specifically, I know there's an antenna amplifier located somewhere, it recently stopped picking up FM radio stations unless you're sitting in the parking lot of the station but I have no idea where the antenna amplifier is located or what it looks like, any help would be appreciated.

Don't have a clue.

But I do have this advice. Even though your system is a Bose, it's a 16 yr old Bose. Many cheap items sold today have better quality.

Why not replace the factory head unit and speakers? this will require you to replace the speakers, and run new speaker wire. It will also require you replace the antenna, but at least you won't have all those separate components to deal with.