Lots of dust and crap will come out of that bad boy when you do it. I think I beat mine into a box that caught all the stuff. Might want to put on a simple dust mask to be safe. Prepare for a boost increase!
You DO NOT want to inhale that "dust"... it is platnium and is very toxic (think of what it has been collecting since day one). Run some water inside the cat before you hit it... and while you are hitting it and into a bucket with about 1" of water to start.
Watch for the boost increase 1-3psi... depending on the style, age and condition of the cat you are gutting. headbang