The IC engine has an inlet manifold (10) made of plastic. In order to reduce the nitrous oxide content of the engine exhaust gases, some of the exhaust gas is directed through pipes (26) and (32) to the inlet manifold (10). The plastic inlet manifold (10) is protected from direct contact with the exhaust gas supply pipe (32) by means of bushes (36) of thermally insulating material, which support the exhaust gas supply pipe (32) against the inside wall of the inlet manifold. These thermally inclusing bushes (32) are made, pref. of ceramic. USE - IC engine EGR system.