Here is what worked for me:
Worried I might damage the powercell with a steel punch so made one out of a piece of roughly 3/8" solid brass rod. Turned a roughly spherical radius on one end and cut the length of the punch down so it only projected a few inches from the engine block when inserted in the injector hole. (It"ll be prone to buckling if you make it too long).
Oh, and two other tips. The powercell will come out of a hot engine easier than a cold and use kroil (or your favorite penetrating oil).