Odd vacuum pressure

[slayer450]

On a cold start she does right up and hold vacuum at 20, I can drive for hours fine but if it shut her off for a few min to grab a coffee or something when I start back up she'll idle a little high and vacuum sits at around 13 for 5 or so min then drops back down to 20. Is this a typical thing or is singing going on that should be fixed?

 

[Bling_23]

Sounds normal at idle. Afterstart enrichment is occuring when you start it up warm so a lower vaccum level at a higher rpm is also normal.