I believe the resonator has a bracket that it mounts into I assume they just put the y in with out creating a tab and welding a piece of angle to secure the length of pipe chances are its rattling because its just suspended. Here are some great pictures hope this helps. I assume they only when Y to straight pipe not the two 45 curves? Looking back at the pics this is just suspended as well. I think a bracket would solve the problem I guess we would need pictures to really understand.
https://www.crossfireforum.org/forum/showthread.php?t=18154&highlight=resonator+removal