I have 3 devices under my car connected to my exhaust, but I dont know what they are or what to do about them?

I have 3 devices under my car connected to the exhaust system. Im unsure about what they are, what I can do about them, or how I can modify these to make the car louder,lighter,and less restricted. The car is not broken and doesnt need repair, this is about modding it. My biggest concern is the last device (3rd picture), because it is big, and most likely heavy. I know the exhaust system will restrict the engine, I also know that the exhaust system has a muffler and a catalytic converter. So my question is   What is this device in the back? How can it be removed/bypassed/replaced/modified to be louder lighter and less restricting? And if I cant do anything with it, what can I do? (the devices are in order from closest to engine to farthest)

Question by fastcar123   |  last reply