[xj] Failing injectors


Last week I managed to fix my ignition system (vacuum etc.) Now I found out
that my car is running better, but still not good. Disconnecting the
connnectors of the injectors, 1a, 2a and 3a that make any difference.
Testing of the ignition shows there is spark in that cylinders, the sparks
itself are black (too rich?).

What do you asmume, can it really be the injectors? If yes, can it be
electrical. Note it seems suspicious to my that all three cylinders in line
(front right) are not working or are working/injecting fuel continuously?