audi s3 p0171 bank 1 too lean, could a decat be the issue?

[arron1995]

I am off to view an 8p audi s3, the owner states that he purchased the car with a stage 1 map on it, he then fit a decat but didnt have it mapped in, he says every 200 miles ish that the eml will come back after being deleted with the following fault code (p0171 system too lean- bank 1).  he said he has replaced the likes of the pcv, diverter valve, brake booster etc and even had it smoke tested and couldnt find anything, what im wanting to know is, could this potentially be the decat due to it not been mapped to the car.