engine miss/injector

5.2/318cu.in 2500 van 94 #7 injector will at time not work causing a miss and then may start working again while driving and if not, if engine is left off for a good period of time, its as nothing was wrong when restarted. I know its the injector causing the miss, because switching the injector wires causes the non working injector to work and vice-versa. If I start the engine cold it may happen. It seemes to me tracing the injector wire to the computer, Could it be the computer? Wire to the computer feed and ground showes continuity. New plug wires, cap, rotar etc.Any hlep would surly smooth things out.

THANKS

had simeler problem with a work van turned out to be a burnt valve and needed a new set of heads.