What can cause the midpipes, second muffler and cats-that whole stretch to vibrate excessively besides being loose and improperly hung. I checked that and it is tight and normal, not hitting the heat shield or anything. The sound is definetly coming from the second muffler to the cat-somehwere along the midpipe.

It is not really a vibration, well it is but it sounds like it is coming from the inside of the pipes. Could my resonator be bad/broken causing too much noise