FAST offers several main harness options to aC - Commodate most customers' needs. The XFI Main Harness is responsible for connecting your XFI ECU to sensors as well as digital dashes, EGT modules, and various optional accessories. The Main Harness also handles communication between the ECU and ignition devices. Main harnesses are available in TPI, LT - 1, LS - 1 through 9 (including trucksuv designs), Modern Hemi, Carburetor Conversions and even Rear - Engine Dragsters and Boats. FAST also offers Main Harnesses that come terminated on the sensor side but non - terminated on the ECU side to allow for a truely custom fit. All terminals, seals and connectors are available individually, so don't hesitate to try your hand at crafting your own custom harness from start to finish.