Thanks for replies. After double checking the sensors and fuses I have removed the injectors and sent away for testing so will wait and see what the results are on that one.
Customer does use supermarket fuel some times but also works shell fuel. I also don't rate the supermarket fuel and is often the first question I ask when a car comes in with fuel problems. But unfortunately the customer only see the price at the pump (my wife included even when I tell her not to)