There is a line at the back goes to the fuel tank vapour release - connects to a little valve thing on the back left of the plenum - you can T off that for a pressure gauge but it can give a small fluctuation when the vapour trap activates - that was putting a hole in my map as the haltech uses the pressure to map - not the MAF - so for a guage its fine
I added an extra pickup to the back of my plenum for the Haltech ECU
Sounds like its going to be great when its done