The Controller plugs into each coil pack along with the crank and cam sensors to provide you the ability to modify the timing curve, set a two step rev limit, nitrous retard or even a boost/timing map! The 6-Hemi Controller is designed to operate with both styled coil packs that are offered on the new engines. A wiring harness for each application is sold separately. Hemi fans old and new will be excited to see that the 6-Hemi Controller will connect and drive the coil packs of a carbureted retro-fit engine!