96 2.4l Ignition Problem

I'm having a strange problem with a 96 2.4L. (70k miles) A few weeks ago the vehicle started to only run on two cylinders. After determining that the problem was electrical, and finding that the one of the plug terminals, boot, and the connector the coil housing was completely corroded, I replaced all of the plugs, boots, and purchased a new housing. After reassembly the problem still remained. I then replaced one, then both ignition coils. but the problem still occurred. (I now have replaced The plugs, boots, coils and housing) I finally took it to a mechanic who diagnosed that the "new" coil housing I had purchased was bad. I exchanged the coil housing and the car started up and ran perfectly.... for two weeks. Yesterday I was driving down the road at a steady speed and it suddenly began to misfire again. I tore down the ignition components, tested everything(for continuity) and everything looked good. Since the problem was identical to before, I went to the Advance Auto Parts and bought a third coil housing, which immediately solved the problem.
My confusion is that the coil housing appears to be a simple connector to me, and I have tested all of the individual connectors on on the one i just replaced with a multimeter and they all make a good connection. Is there something else (ignition control module, sensor) that could be causing this problem, or should I just chalk it up to a faulty batch of aftermarket coil housings and forget about it.




Thanks for any help,
Justin