I had a two codes on my car for catalytic converter replacement: p0420 (rear cat) and p0430 (front cat). I had hoped I could get away with a inexpensive fix like this. Unfortunately, in my situation, the cleaning wasn't helpful. I eventually took my Cats off to examine them and my issue isn't blockage, just old cats. However if your cats are dirty or blocked I could see this being a good option. Or especially on a plugged DPF (diesel particular filter) I could see this being a good option.
The product itself is well made, the hose is plenty long and it seems to have quite a bit of the foaming agent inside the can. I hope it works for you!