i have engine light on. code came in p2177 what it means

I have had the same problem. My 2006 Mazda5 with 120K miles have a P2177 code that would not go away. I replaced Purge Valve, Thermostat, and the coolant temperature sensor. All the related codes went away but the P2177 still remains. There are no symptoms what so ever. I read a bulletin regarding the PCM flush and went to Mazda dealer to ask for the flush but I was told to have them do a diagnostic test. I also replaced O2 sensor. I replaced Purge Valve. What do you think I should do? I am frustrated with this car. Thanks

FUEL SYSTEM IS TO LEAN,CK FOR VAC LEAK TO START WITH