I did mine too,except I went through the end with a hole saw,rather than saw it off,because I wanted to retain the rolled end.Then I took a bit extension,and drilled some 5/8 holes in the first baffle in. That's as far as I went,because it was actually starting to run a little lean right off idle,and I didn't want to mess with the carbs just then.
It don't make it loud,but it deepens the tone,makes it "throatier",and is a hundred percent improvement over the sewing machine! In fact,it's so good,I'm giving it two thumbs up: :finger2: