The Boost Timing Master allows you to adjust the amount of ignition retard from 1° per pound of boost to 3° per pound via a control knob that you mount on the dashboard. This way you can make adjustments on the fly to prevent detonation as fuel quality or altitude and air quality changes up to a maximum of 15° retard. There is a boost pressure port to connect to your manifold and the BTM wires easily to the MSD Ignition Control (Part Number 121-8762) or to OEM style igntions (Part Number 121-5462). 50-State Legal.