i have a mk3 1.4 petrol, i took my air box off to fit an induction kit, i have done this on sevral cars no worries. however, when i opened the air box there was a flap and 2 intake pipes, one standard going to the front to draw cold air and then another which appears to connect to a hose drawing hot air from the exhaust manifold, i have not encountered this before and wondered why it was like this, when i start the car the flap closes of the cold feed and and seems to draw the hot air in instead. i have left the bottom half of the air box on and fitted the new filter with no performance issues, so long story short what is the purpose of it?