The 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 13-14 GT500, the computer is already modulating fuel pump duty cycle and only giving the car the pressure and flow it needs. For tuning, we recommending you reduce the Fuel Pump Voltage Table (under Returnless fuel pump) by 1-2 volts all over and fine tune from there by datalogging. On the 11-14 5.0L Mustang the factory single pump is modulated between high and low speeds by the computer. We recommend changing the high speed threshold in the tune (under Returnless fuel pump) from 0.80 lb/min to 3 lb/min (see below) on blower cars. On naturally aspirated cars this value can be raised to 4-5lb/min for NA tunes and lowered back down to 2-3lb/min on the nitrous tune. The same values would be recommended for cars running E85.
