All fuel pumps are  voltage sensitive, the lower the voltage the lower the fuel volume. Gerotor pumps exhibit a significant increase in fuel volume with increased supply voltage. A Walbro pump's average fuel volume increases over 18% by increasing the supply voltage from 12 to 13.5 volts. The factory harness is marginal at best for supplying a factory pump with enough voltage to perform well. This is why the 'hot wire' modification is so popular. Replacing the factory pump with a high-performance pump can easily double the current demand under W.O.T. pressures.  The voltage drop in the factory harness increases proportionally to the current demands of the pump. has documented tests where the voltage drop in a factory harness has caused over a 25% drop in fuel pump volume. The harness uses heavy 10 gauge copper wire to reduce voltage-drop to very low levels. The factory gauge of wire used is three gauges thinner. The   power feed comes off the back of the alternator where voltage is highest. It then runs through a Delphi weatherproof fuse holder and then to the back of the car. The harness uses three-position male and female Delphi Weatherpack connectors which plug in-line with the factory harness at the back of the tank. No cutting or splicing is required. A Siemens weatherproof 40 amp rated mil-spec. relay is used. These relays have silver plated contacts and are the best money can buy so that you can be guaranteed to have trouble-free operation. The harness has a redundant ground upgrade as it is necessary to improve the harness on the negative side of the pump's supply as well. All the harness connections are crimped using certified Delphi crimpers and are soldered as well. All the harnesses we have seen to date from the competition are not soldered. supplies a spare ATC fuse, black vinyl wire ties, silicon grease and mounting hardware with each kit.