There is a baffle in the silent muffler. It can be removed by calapsing it with a rod through the outlet hole. Then it can be pulled out through the inlet. If the baffle has been removed, the muffler pressure to the tank will be less.

The muffler pressure nipple can be drilled out a size larger to increase pressure to the tank.

The nipple going into the carb can also be drilled out to increase fuel flow to the carb.

Enjoy,

Jim