Much easier way if you have a high speed grinder/Makita 4" grinder. Put a cutting wheel on it and cut through the muffler flange pipe parallel to the pipe. Be careful and only cut through the muffler flange pipe and not the exhaust pipe. I made two cuts at about 9 and 3 o'clock, cutting along the flange towards the actual muffler, most of the way to the muffler. You can pound a chisel/pry bar gently between the exhaust pipe and the muffler and pry the muffler flange away from the exhaust pipe. Go easy and you won't deform the exhaust pipe. The muffler will come off easily once the flanges are spread. This way if you decide it is too loud(it isn't), you can put the muffler back on,pound the flanges back to round, and reweld.
Sam