pound out the insides? or hit it with a hammer a few times so the cage stops ratteling?
Is the rattle internal or is it the heat-shield on the outside? If it’s just the heat-shield it just needs a few little tac-welds to hold it again. If it’s the internal substrate you’ll need to replace or gut it. I’m not sure what “cage” you’re refering to. The inside of a cat has a few substrates, which look like honey-comb structures when you look through the cat. If the rattle is internal it means a piece of one has broken off or one of them is coming loose from the cat housing. Either way hitting it w/ a hammer is just going to make it worse. If you don’t wanna buy a new one just remove it and knock out all the internal substrate material w/ a long screwdriver or bar of some sort. Might make the car sound kinda ricey though w/ the Quad4. But mo powa. 
-TJ
sounds like a honda already the engine is loud as hell
Puddle Growl is the best… grrrrrrrrrrrrrr 
Its prob just a heat shield
cut it off! still rattles
Cats are for pussies… gut it then
dont have way to weld it back on… locla garage wont weld it on for me… i have to cut it off first though
www.jjsautomotive.com :dunno:
did you cut off the top of it also ?
i say punch it out!!
coming from you, this is funny ! 
there is no top… only heat sheild left is mounted to the floor boards.