what if i leave the cooling duct off when i change the alternator 2008 mx5

Yes,. I understand, I bought the car recently and the cooling duct was in the trunk, I researched it and found out what it was ., its a real pain to re install. just needed to know if it was worth the effort., it has probably been off for years., as I or the second owner did not claim to know what it was/ your advise is still valid and one day I will install it .,,,,apparently the alternator was changed and someone thought it was not worth the effort. thanks