I noticed I have a split hose on the passenger side of my car. I have bbk headers and they have a vertical metal tube coming up out of them on the front. from there, there is a metal pipe that leads to hexagonal shaped thing(not sure what it is) from there, there is a rubber hose that runs from the hexagonal thing to down underneath the engine somewhere. The rubber hose is split. Can anybody tell me what this contraption is and how much it would be to replace?

Sounds like the hose from the air injection pump. The black hexagon shaped thing is a one way valve so exhaust gases do not go into the pump. All it's doing right now is leaking air and throwing off the 02 readings. I would not expect it to cost to much.