The converters are very fragile.  Harsh impacts will destroy them.  Find a long metal tube, shove it in there band bust them up.  Make sure you get all the chunks out.  You can also give them a few jarring wacks with a hammer as long as you're not denting it up. 
 
From what I've heard the gutted cats don't sound all that great, but yeah, they're better than plugged cats.  
		
	
		
		
		
		
		
		
		
		
		
	
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