Last yeat I had the same problem:Stuck injector on my Volvo
MD22L. Terrible fight that I finaly won by making an injectior puller: Essentialy a peace of stanchion tubing, a large bolt with a welded screw the size of the injector feed line. The thing attaches to the injector head
and a nut pull up the recalcitrant injector. But the real secret was given to me by my marina owner(Jo Treadwell) who sold
me a can of Nissan
carbon remover. This stuff is fantastic!. It desolve everything in a matter of minutes, in particular all the caked burned carbon deposits around the injector.