Have you got access to another ecu to try? It sounds like your ecu has the same problem that my L8 had and maybe a little more but mine went down on number 2 and 3, it wasn't supplying an injector pulse to them (Well no 2 was dead but no3 had a very weak signal), turned out the injector drivers had gone down so got the injector drive and trigger transistors replaced and it was all good again, I was lucky as a mate of a mate is a genius and sorted it for me