88 Trooper Question

Hi, my trooper is having trouble idling after about 30 to 45 minutes of driving. The RPMs don't like to stay in one place. They jump between
about 1500 and 2500 only when I stop though. A friend of mine said that it might be the vacuume hoses, is this possible or even logical. I dont' really know much about cars, so I have no idea. I'm just trying to confirm his suspicion.
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