Whenever I change/remove an injector, I always run a piece of Scotch-Brite attached to a rod & a drill, up & down the holes..
Engage the stop lever on the inj. pump & then spin the engine over to blow out the results..
Be aware of the copper gasket on the end of the injector.. MOST TIMES they get left in the head & are carboned up & not noticeable..
Then when the new ones come in, either the washer gets doubled up or is left out..
Its BEST to replace them.. & if that isn't an option {for some reason} take it out, sand it down, flip it over & retighten the injector.