Most designs of the time therefore included secondary air injection, which injected air into the exhaust stream. This increased the available oxygen, allowing the catalyst to function as intended. Cat-back exhaust systems replace every component behind the catalytic converter, including most piping, mufflers, resonators, and tailpipes.
Cat-back exhaust systems will include any pipes that run from the catalytic converter to the muffler, the muffler itself, any pipes that may run from the muffler to the exhaust tips, and the exhaust tips themselves. Some cat-back exhaust systems have a muffler delete, which means no muffler is included. This is typically found on vehicles that function primarily for off-road use