There are mainly two big restrictions.
The rings can be removed by grinding the top off.
So that the pressed ring inside comes loose.
Take some time to wiggle it out, they sometimes stick
The airbox restrictions are the snorkels.
You have different ones
-3MA1 are the smallest (midle)
-3ma3 are a touch bigger (left)
-you have the cut version (right)
-And of course the setup with no snorkels (mostly used)
When these restrictions are removed.
You need to re-jet the carbs, as these mod's have a significant impact on the jetting