Gutting your cat.
Get a foot and half to two feet long half 1/2" steel rod or something similar ( Home depot for about a buck ) and a hammer.
Flip the pipe vertically with the front (triangular flange facing up)
stick the rod inside the cat opening and using the hammer keep on whacking the internals until the rod breaks through.
The is made of 2 parts, meaning that there are actually 2 elements inside that pipe, so when you break the first one, shake the pieces out, and continue whacking on it and shaking stuff out until there is nothing left.
Use a light to see inside to make sure that it is empty. When everything is out, you'll see that the inside walls of that (now just resonator) are relatively clear and there is nothing left.
The dual structure of the cat is actually the reason the car looses power when the damn thing burns out. When the cat goes, the debris from the front part of the converter (which takes most of the abuse) completely clogs up the second portion of it, and blocks that exhaust flow.
Your engine simply can't breathe and so it starts to loose power more and more, and if you continue on pushing it, the cat will eventually clog completely, causing the engine to just shut off.