VMP Performance Ford Mustang Fuel Pump Voltage Booster 40 AMP Wire InThe VMP unit is designed to be always on, it's a high efficiency unit and does not require any additional power wires or pressure switches. We do include a 30 amp fuse to replace the stock 20 amp fuse in the underhood fuse box. We hook ours up all the time to prevent any pressure spikes that may occur when a booster is triggered in the middle of a pull by a pressure switch. In the case of 11 14 GT500, the computer is already modulating fuel pump duty