With the exhaust cooled down, take a pull and push and turn on the piping. You may find something else. My output tang for my turbo muffler broke its weld from the inside. It has a nice annoying noise at all rpms. With the LTBs, didn't notice too much on the road. By now with the KM2s, I hear it more.
Also take a look at your shielding as they are riveted to the floor and may have rusted enough to break loose.
