Have ring, will whistle..
One of the first things I did to my truck was remove the silencer ring. Now I'm running with it installed since it's so loud I've grown tired of it! The ring is there to control the high frequency sound at the airbox end, not the exhaust end. Even with mine installed, the turbo can be heard out the exhast. My exhaust is stock, with the muffler removed, replaced with 3" straightpipe, and factory resonator still in place. No drone whatsoever. Stock tailpipe too.
The reason my silencer ring is installed is because I have an Amsoil air filter, with the stock airbox, and the airbox to fender cone has been removed. Without the silencer ring, my ears would start to ring after a long drive. I've removed it and reinstalled it a few times and decided for now I like it better with it in. For now at least!