Super tuning car runs good shooting for great

rmchgr
With a stock type teener I do see what you are saying. They have little to no reversion,so the manifold vacuum will be very high at idle and will hang there for a few hundred rpm before beginning to decrease,gently but continuously.
-But with performance cams, I find that the low idle-vacuum increases as rpm rises to the point where the reversion (due to the late closing intake valve),ends. For streeters(all I know), this is usually somewhere in the 1800 to 2200 area. Then,with no load on the engine,it will hang there, a good long way. I gear my car to run hiway at just above the no-load vacuum peak.
My 367 with a 230 cam,for instance, idles around 11inches, and with no load, the vacuum increases to around 22inches at 2200(24*timing), and IIRC it hangs there for at least 1000 rpm.
Now this data is subject to change somewhat with changes in timing, but it is not drastic. I think the cid/cr and chamber seal have the biggest effects on the size of this Vacuum number, and the ICA probably determines where it peaks,rpm wise. That's me thinking tho.