Someone told me about an exhaust syatem that i would like to use on my mustang but I do not know the exact name, they said that they were called "dumps". What they do is it enables you to have both Dual Rear Exhaust and Dual Side Exiting Exhaust and makes it so that you can go from one to the other with the turn of a switch rather than putting the car on a lift and changing the system every time you want to go from rear to side exiting exhaust.

 

Those are also called 'cut outs'

They really are meant to be opened up and sound like open pipes, because they are put on the exhaust pipe(s) before the mufflers, then when they open, you have what amounts to straight pipes.