GMs often put them on the fan shroud. If there is a vacuum leak then you should be having some sort of drivability issue. If it's a 'vent' hose , or a 'breather hose (for emissions) it may not give symptoms. Maybe it's worth going to a shop and just showing them the hose in question. See how they treat you ....you just might end up stumbling across a shop that you like and will be able to trust for future maint/repairs that you can't or won't do yourself.