F-150 system too lean both banks

I recently had t do a repair to my F-150 for a water leak on the pipe coming out of the intake. 1998 4x4 5.4. I had a O2 sensor fault prior to the maintenance and now have a system too lean both banks. (2 fault codes) I took it to ford and they found a leaking hose (vacuum) and I replaced it. Still same faults even after clearing codes (comes back in a few miles). Started out ran OK when first started, then missed badly as it was warming up and then ran better after about 10 miles. Now after checking everything and flushing intake with sea foam, engine runs OK as it accellerates to about 50 miles per hour then loses all power. Taking out of overdrive does not help. Must stop the vehicle and accelerate again. If floored, this doesn't happen but slow to shift up and low power. Any suggestions? The codes are P0171 and P0174.