We unplugged the harness to the injectors carefully and removed the two bolts holding the fuel rails. Once that was done, we carefully pulled out the stock 19-pound injectors. (Be sure the engine is cool because some fuel will leak/spray out.) Check for errant O-rings that may have come off the injectors and stayed in the fuel rail or injector ports in the intake manifold. Now the 24-lb/hr injectors can be installed, but before doing that, we applied a small amount of pre-assembly lube around the O-rings on both ends of the injectors. The injectors were then carefully pressed into the intake manifold ports.