This kit is designed to install into your C5 and overcome the losses associated with factory wiring to the fuel pump. Because of the heavy 12 gauge (stock is an inadequate 18 gauge) feed, sealed relay and attachment to the output stud of the alternator, extra voltage (on average 2.5 volts) and current become available to the fuel pump, increasing both fuel volume and pressure during WOT, when it's needed most.
Note: Electrical components such as wire harness are not returnable parts. Always refer to a factory service manual when diagnosing engine service problems. You can damage electrical components if the proper procedures are not followed. Be sure you are replacing the correct part.