The problem is the code in the ECU is only written to handle up to 2550mbar. So even if you rescale the reading of the signal from the MAP sensor, if can't represent a value larger than 2550. There is no easy way to make the ECU handle a MAP reading larger than 2550mbar.
Have you ever tried not increasing the 2550mbar value but decreasing the voltage at which 2550 occurs, the sensor is linear and so these numbers should just calculate larger map with higher voltages.?
