Holley Carb problem

You also have a terribly mismatched intake manifold. BUt I don't think that's what the trouble is.

Get a real vacuum gauge and get some readings and go from there. You might not have the vacuum that "mystery gauge" is showing.

Oh and "RV cam" covers a lot of territory. Specifics would be helpful. Even a description of the idle.....a video with good audio perhaps? This IS 2015 after all.