Agree, look for intake leaks first but then look for leaking intake manifold gaskets, (spray carb cleaner around the gaskets and see if the idle increases......) Are you throwing any codes? Any lean condition PO171,PO174 without obvious vacuum leaks would make this almost a certainty...
You need a significant leak to cause the symptoms you describe which you may even hear if it was a split or disconnected hose etc.
I had similar symptoms.
Cheers, William
