This harness is designed for the 1999-2006 4.8L, 5.3L, 6.0L mechanical throttle body engines using an LS1 / LS6 PCM with a 4L60E, 4L65E, 4L70E, 4L80E, 4L85E,or manual transmission. 2003-2006 Engines will require a mechanical throttle body to be installed. 2003-2006 engines which were originally flex fuel will also require Delphi Multec 2 (factory truck style) injectors to be installed. Harnesses do not include connections for the rear O2 sensors or fuel tank pressure sensor but are available separate. Included with this harness is a 10 circuit weatherproof fuse block and GM color coded wires with labels for easy installation. This extended length harness allows eight feet from the back of the intake manifold to where the fuseblock and ECM mount. Perfect for those that plan to mount these components under the seat or in the center console.This kit includes:All new fuel injection harness with OEM fitment connectors and harness breakoutsOBDII connector, mounting bracket and check engine lightRubber grommetMounting hardware**Please note that this harness does not support Flex Fuel USCAR Injectors.** We recommend checking the online manual for the full list of required mating parts prior to ordering.