2005 Megane 1.9 dci injector over fuel

I have got a 2005 Megane 1.9dci, its been at a garage for 6 months and they still can't find out whats wrong with it. The check injector light is on, the car is misfiring slightly at idle and more so under load (2500/3000rpm) the diagnostic computer is also showing that 3 of the 4 injectors are showing an excessive fuel rate. So far the following have been checked/replaced:



-EGR valve

-Injectors themselves have been replaced (twice!)

-ECU reboot/update

-Turbo system has had a smoke leak test

-leak off test on the injectors

-fuel pump

-cam belt checked



Can anyone shed any light on the situation?? please this is getting ridiculous now!