Engine does look quite dirty. Cleaning it up as you go sometimes help, if not show where you have looked. Again how do you Know it is a vacuume leak?
I am an old timer. An old trick is to carefully spray Propane, a very Small amount is the area. When you come across a leak the engine will run smooth.
This is Dangerous. Would be best to take it to a shop that knows what they are doing.
Might be good to a shop that is well known for their service, and buy a little fuel, etc. from them.
The last time I went to the Fast Oil change, they did not put the rubber gasket around the Air Filter. Took it apart later, for a visual inspection, and could see the Black Marks were the air was going around the filter element.
A clean engine is a Happy engine. ?.
God Speed.
Uncle Dave