If i have fault codes P0171 and P0174, whats wrong?

2002 BMW 330
13,000 MILES
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KPETTIT
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I changed out my thermostat last week due to car started over heating. after i changed it out the check engine light came on and i dont know whats wrong. the car runs fine and when i went to get it smog checked today it failed because of those codes. What can be the problem and how do i fix it?
Jan 4, 2012 at 9:43 PM
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RIVERMIKERAT
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P0171-System too lean Bank 1
P0174-System too lean Bank 2
See image
Jan 5, 2012 at 5:09 AM