ORIGINAL: calachie
I filled both pipes with Aluminum JB weld then drilled the holes out small then working them up till I got what I wanted.
That's a pretty good way to do it, JB Weld, good stuff!! Not all mufflers are created equal, I have never had to do anything with the Bisson mufflers but I have had to do some JB work on the Slimlines, not always but sometimes. The Bissons have real baffles in them and create better pressure.