Exhaust manifold nut. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the Exhaust Manifold Heat Shield. Catalytic Converter Nut. Exhaust Flange Nut. Exhaust Manifold Nut. Exhaust Pipe Nut. Part cannot be reused/reinstalled. Bracket. Catalytic Converter. Converter. Converter and U -. Extension U -. Flange. Heat Shield. Included with: Exhaust Manifold.