Well that pipe is connected to a valve and it is known as EGR valve or Exhaust Gas Recirculating valve.
It looks like your Cars EGR valve is malfucntioning and needs changing.
The purpose of this valve is to allow a small amount exhaust gas to re enter the engine. only after the engine has reached a certain operating temperature not when it is cold.
It is good cause it helps keep NOX levels to a low or reduced level which start to occur when temps reach 2500 degrees F and are main cause of pollutants.
It also helps quench the high octane thirst your engine has and keep the octane levels low so you can use lower octane fuel.