+1
Its the pre-heater for air going into the engine on cold starts
It helps the engine heat up faster in colder climates
Flex pipe often breaks and since this is not a required system people don't replace it
From the air filter box to the radiator support is the CAI(cold air intake), it pulls air into the engine from behind the grill, and in front of the radiator
On this air tube will be the connection for the other end of the flex pipe and a valve
When cold the valve will change position and pull in air from around the exhaust manifold which will be air that has been pre-heated by the manifold
As engine warms up the valve switches back to the air from behind the grill
On the air filter box you will see 2 vacuum lines, one line runs to upper intake, the other to this Valve to open and close it
Part inside the air filter box is temperature sensitive, it sends vacuum to valve only when very cold