The standard kit comes with a universal wiring loom for the petrol injectors that is soldered into place. You can use a loom like this, with plugs to simplify the job. The plug-in loom cannot be used with the Junior kit. There are 3 different types of injector plug and each one can be wired in 2 ways. You need the correct one for your engine. This loom is for 4-cylinder engines with Bosch plugs where pin 1 is negative and pin 2 is positive. The loom is copmpatible with most AEB sequential injection systems.