Has anyone installed this gauge. This gauge is mounted when looking at the Duramax engine on the left side. There is a brass fitting with a black cap on it. When you unscrew the black cap, there will be a schrader valve. To my understanding this gauge snaps onto the port there, and measures vacuum between filter(s) and pump. It is sold by www.kennedydiesel.com also there is a picture of it. I would like to know your thoughts on this and if anyone has installed; wouldn't it be better if it screw on, instead of snaps. I think it is good way to see if your fuel filter(s) are starting to plug.