First - thank you to FordPwr for his pictures and advice. I just fixed my DTC P0401 problem by cleaning the coke crap out of my throttle body. The pics in FordPwr's album helped a lot. I posted six detailed pics in my album:
My disclaimer!! I am not a mechanic, nor do I have any training as such. This is just what I did. Miraculously, my truck still runs and I didn't have any screws or bolts left over when the job was done. The fact that I didn't have any parts left over shocked the heck out of me as this doesn't usually happen ...
Here's my hints:
1. You only need to remove 9 bolts and 1 nut to do this job. (Hmm .. maybe that's why there's no parts left over ..)
2. Remove the three bolts holding the plastic housing over the throttle body.
3. Remove plastic air intake.
4. Remove the single nut holding the vacuum hose to the power brakes. Note that this nut screws on to an interesting double ended bolt. The bolt has threads on both sides. You remove the nut first, then remove the bolt using an extended 10 mm socket.
5. Remove the second bolt holding on the The DPF (differential pressure) sensor. Noticed that in FordPwr's pictures, he did not do this, but I found it MUCH easier to clean the throttle body if you do. It's important that you remove these two bolts first as they are difficult to remove when the throttle body is removed from the engine.
6. Remove all the hoses. A light touch with a screwdriver might help here.
7. Remove the last four bolts holding on the throttle body elbow.
Clean the coke crap out and reassemble. I did not have to replace any gaskets when I did this. I did notice that on my 1999 F-150, the gas line was starting to degrade, but I did not replace it yet. I will continue to check it and I might do it in the future.
I had to remove the negative battery terminal for a little while to make the check engine light go away. Now that it's off, it hasn't come back on.