Phantom II Boost Guage
 

were do i tap it in to on the lmm , intake horn ? im just wanting to make sure were to put it have never put guages on a duramax before

You can do it that way, or you a t fitting into the map sensor line and pick up the reading there.
Kenny

got any pics were the map sensor is on this thing im not used to all this extra crap lol

You can drill and tap you IC tubing or drill and tap the intake manifold above the grid heater, just make sure you vacuum out the crap metal.

Heres one pic of pre intercooler boost.

its a matter of preference if you want pre/post IC boost.