No, it will not really work for you. And this is why. Your entire fuel/ignition system is computer operated, and the computer constantly checks the air levels to determing the correct fuel mixture. When the SAFC alters the level, the computer will go ahead and correct the new level back to the stock one. It will pretty much re-learn the curve with the SAFC in mind, therefore eliminating it.
So basically, S-AFC is useless on a 2nd gen altima, it will not do anything at all.
(im sure I made an error in the reasoning above, but thats aproximately why it will not work, atleast thats why it doesn't work for the new Imprezas)