I smell eggs and my Hummer is running slower. I am thinking it might be the catalytic convertor? Is thus it or is this the muffler? If this it is, is there a tool to remove the part attached to the Hummer? Thanks in advance.

 

Looks like that is the muffler. I have 2 catalytic convertors they are more towards the engine on separate pipes. Was experiencing a fluttering sound from the exhaust and smelled rotten eggs. I am going to replace them. Anyone have a suggestion on what replacements?