Ever wondered how the exhaust gases exit the engine and why the Subaru makes that distinctive burble sound?
The noise is all due to the unequal length of the exhaust manifold pipes from either side of the engine ports. This means that the gases are joining at the up-pipe at different intervals which in turn gives the noise.

The illustration to the left shows just how the gases exit the engine and their path through the up pipe to the turbo and finally exiting through the exhaust system.