Small update: since I installed the used Bosch MAF with the adaptor cable, I haven't gotten the DTC, I took it to mild mountains and so far so good, now I gotta take it to the beach and check there.

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.