andi-p

While out in my 2007 Galaxy 1.8 TDCi it developed a slight miss fire which turned in to a loud diesel knock. The nice AA man plugged his computer in and said no fault found and it is mechanical. Got towed home and had a look over it myself, using a long screw driver listened to the injectors and no.3 is different sound when the fault is occuring. I am wanting to know if I removed the injectors to be sent away the be sorted would they need to be recoded in even if they are marked and replaced in the same cylinder.
All help and information much appreciated.