What would you need to fix if you are receiving Trouble Codes P1507 P0171 and P0174 on a 2000 Ford Windstar 3.8 6 cylinder?

P0171 and P0174 (mixture too lean) is a known design fault. Excessive oil is pulled into the air intake plenum above the engine from the PCV tube, and the accumulated oil causes the seals on the isolator bolts holding the plenum onto the intake manifold to fail and leak. The solution is to replace the isolator bolts (current ones have improved seals), intake/plenum gaskets, and possibly some other vacuum hoses. See Ford TSB 03-16-1.

It seems as though your Idle Air Controller isn't responding fast enough. If this isn't working correctly then it can cause the other two codes.

See "Related Questions" below for more on the isolator bolts problems, and more importantly, the fix.