wheres the best place to tap in after the air dog is on?

 

if you didnt get the low pressure light there is a port on the base of the airdogon the side that goes to the engine

 

Is that "Tap" on top of base meaning the motor side?
Or on Bottom meaning the filter side?

Changing out burnt out AirDog-2 pump today if it show up with UPS dude.
System Has 185K miles on it so no issue with original.
We'll see on replacement.

Thought gauge might be good idea.
Is PSI adjustable and how?

Thanks,
GoPostal
Steve French