Originally Posted by sailorbob
2.5 bar and 3 bar MAP sensors produce different voltages for the same pressure and you cannot interchange them without getting fuelling problems. Paul, I suggest you source a 2.5 bar to replace the 3 bar asap.
What he said. Basically the MAP sensor divides the boost range into voltage signals from 0 to 5v, so obviously you can see that that fitting the wrong MAP sensor to the wrongly matched EPROM would mean that the ECU would not be seeing true boost.