Upper Intake Manifold and EGR Valve

For a good explanation of catalytic converters see: http://en.wikipedia.org/wiki/Catalytic_converter Yes, they can clog up and yes sometimes they do need to be replace. I doubt the cat. made the EGR go bad. But the EGR may have gone bad and caused a misfire which could ruin/clog the cat. and/or possibly blow out an intake manifold gasket. But I would take the car for a second opinion first.