TurboWorks exhaust manifold made of cast iron. When tuning the engine, the exhaust manifold should be replaced at the very beginning, because the exhaust gases extruded from the cylinder go to the exhaust manifold, which is part of the engine body, they are then routed to the first section of the exhaust pipe, then to the muffler, or to several silencers in series, and then to the exhaust section of the exhaust pipe. & nbsp