That exact thing happened on my kids 2000 Lantra. Chunk of honeycomb like material came out of Converter and lodged in middle section muffler. Caused intermittent reduction in power as it wobbled around. I found it out as there was almost no exhaust gases when problem occurred. . I,ve heard of some mechanics getting a length of pipe and ramming it up the Converter to "clear" a path. What else would you do on a 13 year old car where a replacement converter is worth more than the car?
The c> What about partially clogged catalytic converter? I had that on a car >