Yes I understand that. I will eventually be getting a Wester's tune. But some are saying that they don't think the new sensors are required to get more than 25 PSI. What I'm trying to say is I think that 25psi at sea level would be the max attainable by the 2.7 bar sensors based on the information found by the GM engineer on Sol Forum
Boost is going to be relative to atmospheric conditions as well as altitude. Standard conditions at sea level are 59F and 29.92 INHG (14.69 PSI).
2.7 bar=39.16 PSI
3.0 bar=43.51 PSI
The PSI boost that you see on the DIC is PSI over atmospheric so 25 PSI of boost is 25+14.69=39.69 PSI, which is over the 39.16 limit of the 2.7 bar sensor.
At a higher altitude the pressure drops, typically 1000 foot increase is equal to a drop of 1 inch of mercury or .49 PSI. Lets say you go to Denver elevation about 5000 FT above see level so the pressure drop is 5X.49=2.46 PSI standard pressure should be 14.69-2.46=12.23. Assuming 2.7 bar (39.16PSI) is the limit 39.16-12.23=26.93 PSI of boost is the max you should see.
So in theory at a higher altitude you would not need the sensor to see a higher boost. However as you increase your altitude and density of air drops the performance of the car's engine drops with it. So a car at sea level may only get 25PSI of boost but it could still out perform an engine that is at a higher altitude that is making almost 27PSI because the boost is a relative value and not a true value of how much air is being pumped into your engine. There are a lot of other factors that need to be considered such as what is the humidity, or the temperature. This is why most people that have an engine dynoed will give temp, humidity, and altitude when stating HP.
Another thing to consider is that the sensors might be rated to 2.7 bar but it might only be accurate to say 2.5 bar (36.25PSI) which if the normal tune only allows 19PSI of boost 19+14.69=33.69psi well under the threshold for the accuracy of the sensor. Also what happens if you take a sensor that is rated to 2.7 bar and run the pressure to say 3 bar does it damage the sensor of does it just Peg and stop reading? I don't know but its something to think about.