Ported vacuum reading

I think I posted this in the wrong thread the first time so here goes again. I was tinkering with my timing today and decided to check the vacuum on the carb. I know that the ported vacuum connection should only have vacuum while under throttle but when I hook the gauge to it I get no reading at all under any RPM. I have a 625 cfm BG Road Demon. My question is shouldn't I be getting some kind of reading at this port?
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