Actually, it does the exact same thing.
The headers are the BIGGEST gain you can make on an NA car.
After the first muffler/catalytic converter, the only difference you can get, is if you put a blockage in the exhaust. Go too big, exhaust gasses will cool though, slow, and cause a restriction.
As soon as you put a muffler/catalytic converter in, you lose the "pulsing" effect of the exhaust, once you lose the pulsing effect, you lose the ability to scavenge.
It is one thing to remember though, that the distance of the first muffler/cat converter from the end of the secondary join CAN affect performance. As you still have pulsing in this front section of pipe, you CAN tune the pulsing to scavenge the secondarys.