Abstract: An insulation blanket is applied around the exhaust manifold of an internal combustion engine to maintain higher exhaust gas temperature in the manifold, thus both to enhance oxidation of unburned hydrocarbons therein and also to reduce ambient air contact with the exterior of the manifold to reduce passive formation of NO.sub.x.

Abstract: A fuel supply system for a gaseous fueled automotive engine has means for damping pressure waves occurring within the fuel line between the fuel tank and the engine. In a preferred embodiment, acoustical barriers, such as annular rings, are secured to the inside of the fuel rail for partially transmitting and partially reflecting the pressure waves so that wave amplitude is decreased. An alternative embodiment comprises an acoustical barrier in the fuel line having a cylindrical section with a diameter larger than that of the fuel line. Baffles, possibly annular rings, within the cylindrical section also serve to damp the pressure waves. The acoustical barrier may also be composed of a conical section with diameters equal to that of the cylindrical section on one end and the fuel line at the other end. Acoustical barriers placed in both the fuel line and the fuel rail also effectively damp the pressure waves.