S/C snowmobile, boost gauge ?????

[87gtNOS]

Hey guys...this is probably the best place for me to ask this.

The guys that are running superchargers and turbos on their 4 stroke snowmobiles are referencing their boost guages off the intercooler..before the throttle bodies (or carbs).
Is this right? This just seems to confuse me...I am used to my car showing vacuum at cruising speeds....when there is no load.
From what I understand, these guys are showing boost at idle...which in my opinion is not true!!

Here is a vid of a supercharged Yamaha, I see his boost is showing zero at idle, again because he is referencing his boost from the intercooler.
Supercharged APEX

I am not yet sure how these systems work on the snowmobiles....just thought I'd throw this one at ya!!

[speedytang]

Question is does the SnowMobile have a BOV which would be open so the gauge might show '0' and some gauges I have had in the past only show boost because of a check valve.

[87gtNOS]

It appears that they do have BOV's.