97 4.0L Ranger 93K
After 3 years and about $1700 my CEL glows no more with P0171/P0174.
After researching this site for info and receiving help from members of FTE I was able to put out the light for P0171/P0174, repair my coolant leak and acheived a much better idle, not real smooth, but a good steady idle.
It was the upper and lower manifold gaskets, however the coolant was leaking on the inside as well as on the outside and sludged up my engine and I had to find a mechanic to replace the oil pump and pickup screen, cost: $650 (And he removed the oil pan without removing the engine somehow, I do not know how he did it though) (a local Ford Dealer estimated $1200 because the engine had to be removed) I cleaned the upper half around the lifters and push rods myself very carefully at that point trying not to have to replace the oil pump but no go but I have a brand new looking top half.
This is a very long story and I had 3 different mechanics try to solve the problems after I gave them approx $1000 for different things and none of it worked.
I live in Maryland and we must pass emissions tests and I had to have the CEL codes corrected, I could no longer put up with the antifreeze smell and I wanted the truck to run and idle better.
I no longer felt confident about taking the truck to a mechanic any longer and was getting too many different diagnosis about why the lean condition existed and none of them mentioned intake gaskets.

So with the research from this site mainly, and with the help of members from FTE, mission was accomplished.

The CEL glows no more, the truck runs great, no coolant leaks, oil looks real good and I am very happy driving my Ranger again. (It's been down for 2 months and I even put it up For Sale at one point.)

And you could work on my engine now with white gloves and not get dirty.