So what is this connector that has been butchered by the previous owner? The red wire connects to the positive side of the battery, and the orange has been spliced into the red wire (in a rather poor job, I must say). There's also a loose black wire coming from the negative terminal, does this belong to anything? The previous owner had a sub in at some point, so I'm not sure which were just leftovers from that.

EDIT: This is a 1991 Firebird Formula 5.0L TPI

Sorry for the tall images!

 

I have 1991 Firebird wiring in my Camaro. I just found out all about that connector when my fans stopped working. I'm pretty sure that smaller orange wire should be a fusible link connected to the positive terminal.

The black wire coming from the negative terminal should be a ground that is attached to a bolt right in front of the battery up behind the headlights.

 

That should be the fuse for the fuel pump, I disconnected it one time not knowing what is was for. Tried to start my car, but it kept cranking, and I realized I had disconnected power to the fuel pump lol.