I know the difference between piggy back and directly tuning the ecu . The shortest distance between two points is a straight line not going around the world to reach your destination. My friend who tunes with the AEM wants to throw up when he hears about E-manage. There are more effective ways of tuning, easier and cheaper$$$. Do some research on ECU tuning . You use the Zemulator or you can use Z control or tune use the binary file. The tools are out there.