Clearly  your bike is crying out for a Supertrapp.

Wolfman, mine did that for awhile. The PO had put a screw in the rear between the small baffle and the large one as a wedge. I took it out and slid the small baffle out. (About an inch dia. by five or six inches long.) Sounded OK so I left it out. Later the big baffle squeaked awhile and later slid out about six inches. Pulled it out, but lost too much power. Put on a Night Train HD muff in an hour for about $40. Not loud, but looks good and power came back. Ground off the front muffler boss (For mounting screw) and slid muffler forward to last screw boss and put 1/4-20 screw through front hole in stock bracket. Had to use big pipe wrench to twist stock muff bracket to line up better with screw hole. Left off OE heat shield, because It looks funney to me to have small muff sticking out of shield. Bought JC Whitney shield to cover header/muff joint. Hope this helps.

Inner wall of the head pipe for?? Loose connection? Sounds like metal on metal right in the arse end of the pipe. Like maybe its the screen or a loose baffle. Just started one day all at once

Has'nt affected power, just annoying so far.
Kinda like the guy today that cut across 4 lanes of traffic and cut me off. Emegency brakeing time. Then pulled up and screamed obcenities at me wanting to fight for about 4 blocks because i gave him "A Look." He dont know how lucky he was, i just ignored him and wondered wheres a cop when you want one....lol
And of course caught every d@mn light and he stayed right beside me. Idjit. I just kept en eye on his front wheel. Road rage.
I needed a supertrapp to drown him out...lol

Then there was the 3/4 ton pickup that forced his way between me and the car in front at a light. I always leave at least a bikes length for an escape route and this dufuss pulled the right front wheel over in front of me untill the light changed. I could of knocked on his passanger side window and asked WTF?

Ever notice how you notice or run into the idiots more on a bike then in the cage.