here is one link for the code
ScanGauge II Xgauge Programming - Mazda Forums
but the one i found before had different variables because atmospheric pressure is not always 14.5 i had to put in 14.2 for my boost to read 0 when the car is off
edit* here is the one with the different settings for different pressures
http://forums.tdiclub.com/showthread.php?t=202184