wierd knocking sound from ecotec...looking for input

[3Rotor]

I've seen  the Fibre glass packing, inside the muffler, being baked and melted to a crispy hard flake,  that then rattles inside the muffler like rocks....  I could not believe it, the guy I made the muffler for, was very  rude about it, and allmost became violent....   needless to say I was stumped, as he assured me the bike on which it was fitted, was dead std.... 

a couple of months afterward, I got from the grape-vine, that he was actually busy fooling around with the bikes timing at that point.... which explained it all...

[silver]

blah blah blah fine, you're probably right, sheesh, don't get so defensive.