Hi!
I'm could be wrong on this, but if you add air into the exhaust in that way you will RAISE the temperature due to adding oxygen to the unburnt fuel, you will reduce exhaust emissions though.

Georges, and Gail,
 On this issue you are incorrect, when we lean the mixture using EFI we are looking for '0' oxygen remaining or complete combustion. Adding air well after the exhaust exits the ports will not "afterburn" the mixture unless there is too rich a mixture to begin with.
Bill Jepson