1995 Mazda Protege Engine sputters and dies

Hello my cars engine sputters and dies if it starts. I have checked that the spark plugs spark and checked the fuel system and cleaned the injectors. I was going to remove the O2 sensors connected to the exhaust, but they are stuck and now slightly stripped. I was thinking that the Catalytic Converter might have gone bad, I did check to see if there was exhaust coming out of the tail pipe and there was. I just don't know much should be there.

What else should I check and or test?
Thank you.