Relieve the fuel system pressure, then disconnect the cable from the negative terminal of the battery. Remove the intake manifold, noting that on 2007 and 2008 models, only the plastic plenum needs to be removed while the intake runner portion can remain in place. Disconnect the fuel supply line from the fuel rail and the electrical connector harness from the fuel injectors by freeing the retaining tabs and detaching the harness from the fuel rail before disconnecting the electrical connectors from the injectors. Remove the two fuel rail mounting nuts and then take out the fuel rail with the injectors attached, being careful not to lose the spacers on the fuel rail mounting studs. Remove the fuel injector retaining clips and take out the fuel injectors from the fuel rail by pulling off the retainer with pliers and pulling the injector straight out of its bore. Discard the old fuel injector O-rings and lubricate new ones with clean engine oil before installation. Install the injectors to the fuel rail and secure them with the retaining clips, then reverse the removal process for installation, tightening the fuel rail nuts. Finally, reconnect the negative battery cable.