In workshops the injectors quite often cause worry-wrinkles, the older the equipment is the more problems they can cause. The workshops prefer to avoid the risks involved with removing them and first ask the customer if they are prepared to take the risk. Not the risk of replacing the injectors, which at between €300 - €400 are relatively reasonably priced. In this case, it's a possible new cylinder head, which would cost about 10 times as much.
Why then are the injectors such a problem? Try to imagine small metal tubes, where on one side the connection to the rail can be easily seen and that reach into the combustion chamber. Only a small copper sealing ring protects the area around the tight-fitting tube from slowly baking itself in. This is why, if this point is leaky, the whole thing becomes so expensive.
As always, here there is also a graded system of solutions. If one of the injectors must be removed and is perhaps joined to its neighbour, then the application of chemicals is definitely an advantage. They don't work directly but they do make the next tasks simpler. Now the lever, which as everyone knows, multiplies the force, comes into play.
Indeed, care must be taken, particularly when using long levers is not only the application-point on the injector to be chosen carefully but also the point on the cylinder head. I can see it in my minds eye, a filigrane, aluminium valve cover, which wiil soon be used as a leverage point to forcibly drive out the injector. A small clicking sound is all it takes, and the cover is cracked.
On the other hand, one shouldn't place the lever directly on threads for the line connection either. To keep it short: one must actually learn how to use leverage, otherwise the damage can very quickly become more serious. The next thing is a tool which is a sort of pipe and is applied to the injector, this can be knocked upwards using a hammer.
Should the injector still not come free, then it's the end of the road I'm afraid, at least if the cylinder head is to be saved. To keep the descriptions from getting too long, here's the provisionally last comment on the subject: a hydraulic device to loosen the injector casings. Whether one can more simply remove the injectors if the cylinder head is taken off beforehand or not, is an open question.
By the way, the work on the hole left by the removed injector is not that easy either. A great deal of residue has been formed, which may even have attacked the seating seal. A lot of work, perhaps also the careful milling of sealing-seat, making sure that the new injector has a good, secure seating. 12/12