Engine vacuum hose diagram

Here are some guides that will help with finding the possible cause of this which is most likely a vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/engine-surges

I attached the diagrams but I suspect it is just a leak around the intake manifold area.

Let us know what questions you have. Thanks