Remove the 2 right side footpeg bracket nuts.
Remove the 2 bolts that hold the header to the cyl. head
Remove the 2 nuts that hold the muffler to the muffler bracket /they are between the muffler and the rear wheel/
Remove the whole pipe assy
Remove the heat shield - 2 philips screws and a bolt for the heat shield clamp
Losen the muffler clamp and spray liberaly WD40 in the connection between the header and the muffler.
Twist, turn and pull on the header and the muffler untill
they separate.
   You can try to just take apart the heat shield clamp and losen the muffler clamp.After that You take off the 2 nuts that hold the muffler to the muffler bracket .Pull apart the muffler from the header. But in a long run it will be easier to go the first road. Seems more work, but it is easier.

I did get my muffler off without removing the whole exhaust assembly, but I needed help. My frieed pulled on it, out and back,  while I held the bike in place, after I loosened the appropriate bolts & nuts.  No damage.

Now if someone would figure out an easy way to get the tank on and off...  what a PITA!    On my other two bikes, GT removal & unremoval is very easy...