Intermittent Problem. Electrical?

I have a 1997 Plymouth Grand Voyager SE that has developed an intermittent problem (3.0 engine, 131000). Driving at highway speeds (I've never been aware of it happening at speeds less than 40 miles per hour). On some days (not every time I drive) I feel a split second hesitation (accompanied by an occasional squeak). It may occur every few minutes for the length of driving time. But many times upon stopping somewhere, restarting and resuming highway driving speeds (during the same day) the hesitation stops and does not come back. In the last week this problem seems to have advanced a step. Driving down the highway with cruise control set at 70. Suddenly what feels like a split second power loss. The speedometer needle will flop to about 50 but will immediately jump back up to 70 (but I have to reset my cruise control because it disengages). None of this happens consistently. Also, my 'service engine soon' light may come on and stay on for several days and then go off and stay off for several days. It is becoming really frustrating trying to figure out what is going on. I don't know if it has any bearing on the problem, but I have started having some small problems with my ignition switch. Such as.A small amount of 'play' with the key inserted. The key will not turn into it's 'backward' position (used for playing my radio when I am sitting somewhere without the engine running).

It doesn't make any difference whether the cruise is on or off when it is acting up. Have tried driving it both ways. Also, have already had a diagnostic ran on it. Codes showed three plug wires and the rotor needed attention. Which were all changed, plus the distributor cap replaced. Also have ran the code sequence and checked the codes myself with the manual. The only thing that keeps coming up is a code 43 and then a second 43 comes up. Which deals with primary ignition coil circuit one, two and three. But all the plugs have been pulled and checked. They are fine.

jw