LTFT zero on mazda cx7 2008 + high fuel consumption


Mazda, CX-7 2008 2.3L Turbo
Hi I have this Mazda CX7 2008 2.3L turbo, and am experiencing the following:

LTFT is zero, no matter what conditions I drive the car on.
Gas consumption is high: ~22L/100km (10.6 MPG)
DTC P2006: Intake Manifold Runner control stuck closed bak1 a)
Car surges/hesitates while accelerating

I checked the MAF and seems to be fine (.7V at ON, 1.4 at Idle warmed up, however at 2500 rpm reads around 11 instead of 8.6 as stated in the service manual).

Had the dealer do maintenance such as spark plugs, injectors cleaning and throttle body cleaning.

I checked the Oxygen sensors and still cannot determine if the readings are correct or not.

No CEL saying there is a rich or low condition, nor saying there is issue with any of the O2 sensors.


So, my questions are: What is making LTFT be stuck at 0, and does this affect gas consumption? As well, how to improve the gas consumption?

Thanks and regards