The air inlet and exhaust system components are: air cleaner, inlet manifold, cylinder head, valves and valve system components and exhaust manifold.
When the engine is running, each time a piston moves through the intake stroke, it pulls air into the cylinder. The air flow is through the air filter, inlet manifold, passages in the cylinder head and past the open inlet valve into the cylinder. Too much restriction in the inlet air system makes the efficiency of the engine less.
When the engine is running, each time a piston moves through the exhaust stroke, it pushes hot exhaust gases from the cylinder. The exhaust gas flow is out of the cylinder between the open exhaust valve and the exhaust valve seat. Then it goes through passages in the cylinder head, through the exhaust manifold and out through the exhaust pipe. Too much restriction in the exhaust system makes the efficiency of the engine less.