I can't get mine adjusted, either (Kompact Dual Port). The first one blew apart because I loosened it too much and was still getting low boost flutter. I have a new one on, but it does the same thing. Annoying.
Sure. I had a 3" Magnaflow single in/out muffler replace my resonator and finished it off with 3" piping and no mufflers. It's sounds good (to me) and isn't loud.