2002 Mitsubishi Diamante P0171&174/P0401

Computer problem
2002 Mitsubishi Diamante 6 cyl Front Wheel Drive Automatic 190k miles

have 171 &174 codes. Reasonabally certain no fault with ignition or fulel system. Fuel pump fuel filter all less than 4months old. Also pressure regulator. Nobody can find any leaks head gaskets etc.I cant find any cracked. Hoses help! P0401 new egr valve new map sensor. Where the ##**%## are these egr passages located I keep reading about located. Diamate owners unite one of your fellow peers is in trouble. In spite of these issues the car runs &behaves just fine.