J5:

The 4.9V which you observed when pressurized is usually the max output, irrespective of the designed range (in atmospheres). The difference between a 1atm sensor and a 3atm sensor is in resolution. The max output of both is 4.9V.

If your pressure regulator is sensitive enough, try slowly increasing pressure until the 4.9V point is reached, then note the pressure at that voltage. You can then plot the three points, and check for linearity.