Depending on your engine and type of vehicle, the exhaust manifold can either be a set of pipes or it can be a cast iron manifold assembly. Essentially the exhaust manifold takes the burned exhaust gases from the engine's cylinders and ejects the gas through the exhaust system and out through the car's tail pipe. The exhaust manifold gasket seals the surface of the exhaust manifold to the surface of the cylinder head, preventing leaks in the system. Over time, the constant expansion and contraction of the components (caused by constant heating and cooling in the engine), may cause the gasket to leak. These leaks can be hazardous as hot exhaust gases escape and can damage other components in the engine compartment. A leaky exhaust manifold gasket can also impact engine performance. So replace your gasket and regain back lost performance.