The gauge shows directly the values that your ECU is spitting out over obd2. There is no magic involved, just raw data from the car. We may add a speed calibrate feature if enough people would like to change what the car is reporting over obd2 for speed.
If you peak inside the "quick start guide" printed manual that came with the gauge, you will see a complete diagram of the wiring.
As for boost, obviously if you have a JB4, you need to use the supplied (with group buy customers) jb4 connection kit and configure the boost to read from this. The little white paper in the kit has the instructions. This let's the gauge read the boost before the jb4 "fakes" it. If you need more details you can e-mail me at
rick@p3cars.com, but basically you send the 0-5v output of the T-Map into the blue wire on the gauge harness and config the gauge to bSt.P
-Rick