Ford Repair: 97 light duty 250 missing, mechanical issues, fuel injector

Question
QUESTION: I had a tune up in Dec 08 because the 4.6 was missing.  The mechanic changed plugs, flushed the injectors and reset the Check Engine light.  Now after a few K the miss is back and the check engine light is back on.  What next

ANSWER: First I would like to apologize for not getting back to you sooner. I had some families issues that required attention and was away from my computer for a few days. Pull the trouble codes, I assume that the check engine light did come back on. Also, you may be at odds with this next part. Find another mechanic. Trouble codes should never be erased, honestly, I wish that the option was not so readily available. The codes will go away  on their own, only after the mechanical issues have been resolved, and the vehicle is driven through the proper drive cycles. Deleting the codes only makes trouble shooting harder if the problem is not fixed correctly. The trouble codes will tell you which cylinders are misfiring, which may point to one of the coil packs being defective.

---------- FOLLOW-UP ----------

QUESTION: I replaced one of the coil paks yesterday but still missses. Then swapped the one removed to the other side.  Still misses. Do I need to change both?

Answer
Have the trouble codes pulled. When you say still misses, are you referring to the original cylinder that was misfiring? If so, you are possibly looking at a faulty fuel injector. If I don't see a reply, I will send a follow up with my email to correspond that way.