This Ignition and Engine Harness is required and sold separately from Pro-Flo 4+ Chevy LS EFI System #36130. This Harness is specifically for Chevy LS 58x Crank Cam Reluctor applications where Crank Sensor is grey in color and located at rear of block behind starter and Camshaft sensor is located at rear of block on top. This harness connects into Pro-Flo 4+ Main Harness Connectors labeled Engine Position and Ignition. Harness has connections for Coil Pack Harnesses, Crank Sensor, Cam Sensor and Engine Ground.