BLOCKED? it can only block itself if you somehow dump raw petrol in it on a hot running engine, otherwise its pretty much impossible to melt it to blockage. You cant block it with carbon soot too, as you are driving a petrol engine, and the convertor on a petrol engine gets VERY VERY VERY HOT. No carbon soot can survive in it - imagine furnace heat.
If you remove this - your car will perform and sound like the stuff you flush down the toilet after relieving yourself.