between piggy back and stand alone. I am learning the nissan ecu tuning . No need need for extra hardware like the E-manage BS. You can change the code directly instead of fooling it with a piggy back. I had an afc which is form of piggy back. I've seen the AEM in action tuning 800HP Supras. Don't try to argue that the E-manage is good tool for tuning for the money.