Advance and transfer slots

Read my comments in the MVA debate, in the General Discussions forum.
You gave the engine more idle timing, & the idle rpm & vacuum increased. Both are indicators of increased engine efficiency. The engine is making more hp with more timing, hence the rpm increase.

Often with big cams, the vac is insufficient to pull in the PCV pintle; acts like a big vac leak. Not realised because it is out of sight, out of mind. Because it pulls more air, t/blades need to be closed further. This could be your problem; just this week, I fixed a 360 engine that had this problem.
You can buy an expensive adjustable PCV.....or the simple, cheap trick that I use. A loooooong time ago I measured/calculated the PCV opening at idle. Equal to a round hole of 7/64-1/8".

Simply get some round 3/8" stock, alum, old bolt, etc & cut off a length 1/4-1/2", not critical. Drill a 1/8" hole through it & push into the PCV hose. Job done.
If the pri blades still close too much, you have an air leak or too much air getting past the sec blades [ reset them ].