XC90 D5 2009 Barometric sensor issues?

[Vulpes]

I am diagnosing the ECU in an XC90 D5 2009 as the barometric sensor seems to be causing trouble, car drives perfect in the capital (San José, Costa Rica), however, as soon as the car is driven to higher or lower elevations, it starts throwing MAF and EGR codes: MAF signal too high, MAF signal too low, EGR flow too high and EGR flow too low. These codes are thrown randomly when engine braking, and alternate between "EGR flow too high/MAF signal too low" when driving in high atmospheric pressure areas (i.e. when going to the beach), or "EGR flow too low/MAF signal too high" when driving in low atmospheric pressure areas (i.e. going to a mountain). The ECU has been several times remapped by a local tech in order to increase power and attempt to solve the problem, the DPF and EGR have also been supposedly deactivated.

My question is: If I connect the car to VDash and purchase a Stage 2 remap, is the remap based on the original map that is downloaded from the ECU? Or is it based on a general map the lads over at D5T5 use?

I would like to try remapping the ECU with VDash before replacing it in order to discard potential issues with the remap, however I am worried about the local tech's map interfering with the remap.

[T5 T6 Schnappi]

@Vulpes have you "blanked" your EGR? And check/clean your MAP sensor. Do these errors appear with the original factory map?
D5T5 uses generic files from Obbe-Tuning. Custom tunes would require datalogging/dynoing.

[Vulpes]

@T5-T6-Schnappi Thanks for your reply!
EGR has been blanked and MAP has been cleaned.
I am completely unsure these errors appeared with the original factory map, hence I would like to try remapping first.

I will proceed to remap the following days and post updates.

[Vulpes]

Ok so I loaded a Stage 2 + egr+dpf off remap and MOST problems were solved except the barometric issues, so its safe to say there is something wrong with the baro sensor indeed.
I took the car high up into the mountains and in random intervals when I was not touching the throttle the "MAF sensor reading too high" DTC popped up.

Is there anything I should check before replacing the ECU?

[T5 T6 Schnappi]

@Vulpes did you do some live data readings while driving? If you see a constant barometric pressure of 1023 mbar regardless of the real outside pressure, you should check the wiring for brittle isolation and the connector of the MAF for corrosion and loose pins,and if they are ok, replace the MAF. You should also check for vacuum leaks, especially at the engine mounts.
Do you run the original air filter box, or some aftermarket cone filter crap?