I spent a while looking into this myself.

The main problem is that the MAP sensor value is stored in an 8bit variable. This variable has a maximum value of 2550mbar, because it has a scale of 10, and the maximum value an 8bit variable can hold is 255. So even if you change the sensor to one that reads higher and update the sensor voltage to pressure conversion map, the ecu can't store any value higher than 2550mbar.

If you want to change the variable scale or offset to another value, then you will have to find every other pressure value in the ecu and update them as well. You could also change the 8bit variable into a new 16bit variable, but then you woul have to update all places using the old 8bit variable to the new 16bit variable, and change the 8bit assembly instructions into 16bit instructions. Both of these approaches would be very labour intensive.

The other option is to not rescale the sensor voltage to pressure convesion map after upgrading to a higher reading MAP sensor. If you do this the ecu will believe you are running less boost than you actually are. You can get away with running this way if you tune any important maps referencing the MAP variable to be in line with your new sensor. There may be unknown side effects to underscaling and having the ECU belive you are running at a lower pressure than you actually are.

Hope this helps.

I have disassembled just about every function that reads in sensor data in the ME7. I was also very surprised that the MAP value was being stored in an 8 bit variable. The main problem I found was that the internal scale of the MAP variable limits the maximum value to 2550mbar. If you were to rescale the variable to allow for storing a higher pressure, you would then need to rescale every pressure constant in the ECU. All pressure constants in the ECU seem to use an implicit scale of 10.

Tony, you are correct.  The map sensor goes through a y=mx+c normalization and then is stored as a byte.  

What is worse is that "requested boost in front of the throttle body" is a byte too  

All in, that is a lot of work to change for minimal gain.

This would be why the APR 3+ files all clip at 2550 and then just rely on the maf readings after at high boost.  But then again, they just run it pig rich to be safe anyways....If it were easy, I'm sure they would have done it.

On a side note, I see many TDI mappers swapping the pressure sensor.   

Here are the maps to rescale a MAP and install anything you like

gradient for manifold pressure sensor - DSSGRAD - hpa/Volt
offset for manifold pressure sensor - DSSOFS - hpa

In my car I have install 300Kpa maps instead of 255Kpa stock!

Tony says above that the value is stored in an 8bit value though so I don't see how you could just toss in a new sensor and change those calibrations. Seems it would just clip at 255.

in 1.8T engines works perfectly!