From the COS tutorial, page 14:
Configuring a 2 or 3-bar MAP sensor
When the key is on but the engine is not running, the MAP sensor reads the barometric air pressure, usually 101kPa (14.7psi). When tuning in high altitude areas it is worthwhile reading the MAP values (using EFILive’s Scan Tool) at key-on with the standard 1-bar sensor to obtain the barometric pressure at the current altitude.
After fitting your 2 or 3-bar MAP sensor, you must rescale the MAP sensor.
Engine Diagnostics->MAP->Parameters• {C6301} MAP Sensor Scaler:These values will get the MAP scaler’s value close to what it needs to be, you will then need to adjust it (by small amounts) until the MAP sensor reads the same barometric pressure that your standard 1-bar sensor was reading at key-on, engine-off.
2-bar sensor: 190
3-bar sensor: 288
Logging boost levels in the Scan Tool must be performed with the PID ‘SAE.MAP’.