Vacuum leak can occur from any of the vacuum hoses. It can also be from leaking intake gasket.
If you have already checked the hoses, it will be a good idea to check if the intake gasket is leaking.
With the engine at idle, spray carburetor cleaner into the base of the manifold. If there is a leak the engine will react to the chemical and will idle higher, then it will go back down after the chemical gets burnt off.
Here is a helpful guide:
Also it might be good idea to clean out the throttle body as dirty and debris in the throttle body can create idling or engine running rough issues.
I have attached diagrams for your reference.
Please let me know if you have any questions.
Images (Click to enlarge)
Tuesday, November 30th, 2021 AT 1:15 PM