I don't see how a cat could damage your heads.  My cats never go near them.
 I also think drilling a hole in your cat will cause a leak of the red
fluid inside.  Besides, they are a big help with the mouse problem
mentioned in several other posts.

If the problem is a clogged catalytic converter causing your engine to
overheat, BUY ANOTHER ONE.

Bill (SE Arizona) (Bill@freeholder.com) HTTP://www.freeholder.com
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You can't do everything, but you can do something.
You can't help everyone, but you can help someone.
Even one candle helps to push back the darkness.