Engine surge

I would get a can of throttle body cleaner and clean out the throttle body. Be sure to get both side of the throttle plate.

Understandably so, however, Just having that sucked in doesn't clean both sides and all around the throttle plate. Especially in the edges where it pivots. If you are not familiar in how to use the product then you can cause cylinder damage with a lot of spark knock. You can also spray around the intake with the cleaner to check for any vacuum leaks.

You will usually get smoke out of the tailpipe. It's the carbon being washed off and burned.

I think you are on the right tack when you said it was a vacuum leak, here is a guide to help find it,

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

Let me know what you find