Fluctuating AFR for MY06 Auto

[-=HaZ=-]

Hi Guys,

The car has been on the dyno the last few days and the AFR seems to be wildly inconsistent. Dipping as low as 11 and going up to 13.3. The car is an auto, and the tuner was concerned that there may be an issue with the Mass Air Flow Sensor; I bought a new MAF original Denso Subaru OEM part, however the wild dips and peaks continues.

The car had an MRT Unifilter oiled foam panel filter and the tuner suggested that it may have contaminated the MAF, leading to the unstable AFR. We have removed the panel filter, cleaned the MAF, however the AFR are still very inconsistent. The tuner said it may just be the auto and the way it operates as he says he has never seen this behaviour on a manual car.

Unfortunately he hasn't tuned an auto Liberty before and I have no idea what is considered normal, this being my first Subaru.

BTW the Front O/2 sensor is brand new and so is the MAF. The car also has a brand new AVO 265L/Hr fuel pump, and the pressure is good.

Can anyone advise if what we are seeing is normal for an auto Liberty GT? Can anyone explain this behaviour? Do I have to replace the MAF for the third time!!!???