CODES P0171 P0174

2000 Ford Ranger

I have a 2000 ford ranger w/ 156,000 miles 4.0 ohv w/ 4wd. It has codes p0171 p0174. I have changed upper and lower intake gaskets, all o2 sensors, pcv valve, fuel filter, coolant temp sensor, air intake temp sensor, and vacuum hoses. I finally took it to ford and they can't even figure it out. Please help, thank you
June 14, 2007.

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