As I stated before, rust in your tank is the problem and it was confirmed by Ford. Even though it's running better now your problem will come back. Instead of having Ford replace the tank why not seal it yourself? Here's a web site that has tank sealers that look better than others
Gas Tank Sealer - Gas Tank Liner - Best in the World - KBS Coatings. We used to seal old motorcycle tanks that had rust in them and stuff like this works. You'll need to drain the tank and remove it so I'm not sure how difficult that would be but I'd sure consider spending a hundred dollars and some sweat equity before letting Ford get into your bank account.
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2001 National Tradewinds 7370 300 Cat
2011 Jeep Wrangler Unlimited Sport
Officially fulltiming. The Journey Begins