He only ran the injector buzz test and wants to replace injectors?? I would never replace injectors based solely on the buzz test, if the injectors did not respond or "buzz", you more than likely have some issues either with IDM, UVC wiring(most common), gasket, or engine/chassis harness. Do you know exactly what codes were retrieved after the buzz test? They may help narrow down the exact cause, but with four injectors not buzzing, with two on each bank not buzzing, either UVC harness issues, or the engine has not been maintained the the oil is sludged in the injector not allowing proper movement of the poppet so you cannot hear it.
Buddy
Buddy