Moriwaki 4-1 exhaust

Hi,
Found a Moriwaki exhaust on Croooober for my 500 racebike. 
When I look into the collector it looks like 4 conical restrictors.
This is not a racing exhaust so maybe it’s for damping noise? Or can it be something to increase performance?
 

I would guess it's to boost low end torque ??

I guess it needs to be perfectly tuned to the engine then. 
I should run it on dyno and then remove it to compare 🙂

It seems like a weird place to put an exhaust restriction. Most of the systems I've seen have the restriction at the front of the baffle in the muffler.

Kelly E wrote:

It seems like a weird place to put an exhaust restriction. Most of the systems I've seen have the restriction at the front of the baffle in the muffler.

Yamaha also put the "EXUP" valve in the collector ?