I just redone my injector inserts and O-Rings and it wasn't too bad a job but then again I was sat on the living room floor! I imagine on the car you'll struggle to do it. Those inserts are brass and to be fair mine were just grubby and looked a bit fooked. it's the plastic holders that can cause problems as they can go brittle and break up after a bit. new injector o rings and then try them

don't forget the little O-rings for the bottom of the injector
When I put my injectors back in I was amazed at how hard you had to push to get them to sit properly a bit of spit on the big O-ring helps things along nicely
