I uncrimped The box and removed this out of the center.
I did this before on my 110 and 115, so this wasn't new to me. It was a pain the first time, but after you do a couple, it really isn't a bad. To anyone that wants to attempt it for the first time, I recommend a small 90 degree prybar (tool trucks call them lady foot prybars, or rolling head pry bars) and a set of good channel locks such as Knipex pliers. Start it at the open section and work your way around. I get the lip just off the back piece all the way around, then using a quality pair of channel locks, I bend the lip up to 90 degrees so you can lift the front off. The biggest thing is not to tighten the vise too much as it will really distort the back part of the muffler. Also, prying really hard, or trying to get the lip at 90 degrees with a prybar can put dents in the front cover. Or if you are really gifted at welding/brazing thin steel, you could cut the lip off with a cutoff wheel or grinder, then braze the two sections together. I have not tried that, yet. If you use a set of cheapo pliers, you can mangle the steel and it will slip off more than once causing you to curse more than once, ask me how I know!
I grinded the tab off of the end of the baffle that was 1/4" thick and looked kinda like the exhaust gasket.(it was tack welded on the top and bottom) It went behind the tubes that go thru the muffler. I did this because without the spacer, There would be too much space when you tighten the muffler down. It would pull the center of the muffler in, and the bolts might possibly have bottomed out on the cylinder. I have another 6401 coming sometime next week, I will try to take detailed pics and do a seperate muffler mod thread on it. That might explain it a little better.
-Steve