I have been trying to sort the P0171 code from about a week after I got the car, I have now replaced the Maf sensor, and the first lambda. the light is coming on anywhere between 50 and 200 miles at the moment at quite random times.
I have bought the Tourque ap and a obd2 bluetooth sender so am now recording sensor information for every drive. As soon as I can find out how to get the video up still showing the sensor information, I will post it up for you guys to comment on.