Being that the best way to check an injector is to bench test it, you may as well pull the injector and replace it. All the evidence points to the injector being faulty. While you're pulling the injector, just do a quick visual check on the harness to make sure it's not the issue.
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I attacked the 4.6 150 this morning. Started by getting a new coil for the cylinder 5 misfire. When I removed the bracket for power steering canister to access the coil below I found two broken wires. It runs from the harness and plugs into the front bottom of the fuel rail. I haven't a clue what it does. I soldered both wires, taped and retaped. Installed the new coil. Runs fine in the garage, no diagnostic lights. Hope this solved the problem. I have not driven it yet (we're in the midst of monsoon like weather) but am optimistic with no diagnostic lights on the dash. Thanks for all the suggestions.