Help Needed!

Car: Audi a4 estate 2007 S Line Quattro 2LTurbo Petrol

Problem: Trying to sell my Audi however recently the Engine management light has come on.
The code throws up ' Running too lean when idle'

Parts already changed by various garages;

1. 06F-133-781L – Check Valve with Pipes
2. 06F-129-101R – Valve
3. 07K-905-715F Ignition Coil
4. 33230 – Oxicat

Another valve has also been replaced, lost the garage doc...

The car is now running at 950Revs, it was running at over 1k before. The car runs like a dream with no indication of a fault. After resetting the fault and turning the light of it takes about 30MILES before the light comes on. (Much longer then you would expect)

I am leaving the country soon am and desperate to sell the car! If anyone has any suggestions, it would be Ideal.