as an addition to what tony said above
when you refit the injector use a torque wrench as overtightening can be a cause of lack of power by stressing the injector body

not the best job, 3hrs. can be a bit tight for one bad one, if you end up doing all four depending on how gummed up they are it could take 4hrs. upward, i alway renew the plastic seals at the top of the injector tube in addition to the copper washers & generally end up re-cutting the seat.


Steve