I don't think they are vacuum ports
Most likely you are looking at coolant ports that were used to prevent icing in colder climates
factory heater hoses each had a "T" with a smaller hose going to one of those ports, this circulated coolant around the front of the intake where air velocity is high to keep it warm, this prevents moisture in the in coming air from freezing, called icing which can cause running issues
These "T's" would crack and leak so many people just removed this pre-heater and used regular heater hoses with no "T"
And removed the smaller hoses, you can put rubber caps on the ports so they look "finished" but its not required
In Florida you wouldn't need this type of pre-heater, but it was stock on all 3.0l's for quite a few years
They also had heated PCV Valves
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