Hi Sir or Madam, I am John Mc, a Ford dealer technician.I hope I can help solve your problem quickly and accurately.
Use a noid light and check if the pcm is firing the affected coils. If not replace the pcm. Ford has had some problems with the coils going bad and then causing the coil drivers in the pcm to fail. Since you have replaced the bad coils and the plugs if the coil connector is not pulsing then you have a bad pcm. If you don't have a noid light here is another way to check the coils. Disconnect the coil. With the key on and engine off use a test light and see if one wire has power. Now connect the test light to the positive side of the battery and check the other wire with the engine running. It should pulse, if not replace the pcm.
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Yes you can use one from a salvage yard but you will have to take to a dealer to have it reflashed and to have the keys programmed to it. You even have to do this with a new one. I would suggest finding one as a new one is over $800! I just did one for a friend with this problem a few weeks ago and my cost was ridiculous!