I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
What I did when I first got my car was to remove the 4 nuts at the back of the cat...pound the honey come out with a big punch and hammer...and then used the shop vac to remove the chunks of honeycomb. Test pipe isn't needed. One of the neighbours asked me what I was doing. Told him I was vacuuming my exhaust. Gave me a blank stare and walked away.