And having been in the trucking business all my working life, I have heard for the first time that servicing injectors is a dodgy business. In my career I have seen thousands of injectors successfully serviced over and again. Unless we're talking about the tip only which is generally replaced when the injector is serviced.
Servicing is not dodgy.
However a statistical analysis showed that the failure rate of injectors that had been removed and serviced then replaced was significantly greater than that which were allowed to run. It is a long time ago but my memory says the data came from the Midland Bus Company and a London company and was from large number of vehicles and a decade or so of records. The engines would almost certainly have been Gardiners.