Fault code 171 on 95 Mustang

I have a 95 Mustang 3.8, V-6. It continues to show a fault code of 171. I have replaced all O2 sensors, MAF and EGR, but still the fault code remains. I started to replace the intake manifold gaskets (i.e. Windstar), but the dealership partsman said the 95 Mustang 3.8 is a different configuration from the Windstar. Any suggestions?:banghead:

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