The mufflers I have modified were square box devices. I have done Homelites, McCulluchs, Weedeaters, etc. There was a baffle in everyone that I removed. The bolt-on ones had tubes that surrounded the retaining bolts to keep the muffler from collapsing when the bolts were tightened. These tubes need to be left in the mufflers.

The other tubes I was talking about are the exhaust outlet tubes.

Enjoy,

Jim