I give up..

I have been working on the exhaust mod on my '92 Honda Nighthawk 750.
I got as far as getting the rivets drilled out. However 19 years of heat and crud have welded the funnels in. So even with the back side of the rivet heads loose inside the muffler, I opted to re rivet the funnels closed.

I did run it with the rivets out.
It did make it louder, but it was a buzzy wraspy louder. The reduction in back pressure also leaned out the mixture making the exhaust hotter. This started blueing the chrome pipes.