Exaust intake leaking
It's exhaust manifold. There are two manifolds, the intake manifold in the valley between the cylinder heads, and the exhaust manifolds, one on each side of a v figured engine.
And, yes, a leak in the exhaust or the intake will make it run lean. If the leak is close to the engine, it can do harm to the valves, too. There is a gasket between the exhaust manifold and the engine block. Likewise, there is an intake manifold gasket between the intake manifold and the block.
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