If you need to troubleshoot injector problems, this easy to use six piece kit allows you to check for injector pulse on many EFI equipped vehicles.  Simply unplug a fuel injector and plug the appropriate lest light into the wire harness connector. If it flashes while cranking/running, you have injector pulse on that injector lead.  Includes test lights for GM TBI, Bosch PFI, Ford TBI, GM PFI, Geo TBI, and GM SCPI equipped vehicles.