1999 Ford Expedition Ford codes P0171 and P0174 still comin

[quote:e233c3ccf3="short_angel_101"]Engine problem
1999 Ford Expedition V8 Four Wheel Drive Automatic 153000 miles
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We changed out the MAF sensor. But after a day the light came back on and it is still those codes. Any suggestions?[/quote:e233c3ccf3]

check for a vacuum leak
that will effect the two banks

i had that problem and it was one of the oxygen sensors, there are four of them. two on each side of the y pipe, they come up as bank 1 and bank 2 on trouble codes.