So pi$$ed of rite now
Pulled No2 injector today to replace the seal as it is leaking diesel and found the O ring is damaged.
Couldn't do anything about that as I didn't have one to replace so put the washer seal on refitted the injector and more smoke and noise than before and no doubt diesel will be gushing out if I drive it now.

Should a damaged O ring make that mush of a difference?
I thought the brass washer seal was what did the job?

The copper washer is what does the sealing, but the surface it sits on needs to be microscopically clean. If there is a buildup of carbon where the washer sits in the head then it wont seal properly. Various tools are available to clean or recut the seat where the washer fits.