Replaced MAF sensor and ODB code still comes out as P0171

I bought my 2000 nissan sentra about 6 months ago and for the first few months the car worked ok but then the engine began to idle a bit and my SES light began to come on and off. finally one day it decided to stay on i took it to the dealer and they told me that the MAF sensor was messed up so i got that replaced the light is now off but the car idles ALOT more than usual and in keeps giving me the P0171 code :banghead:. Has anyone found a solution to the problem? any info will be useful thanks!

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