Vacuum readings

[85Silveradoin04]

So I did a ported to manifold comparison.

At idle (1000RPM) with the dizzy on ported vac, I'm running 19 - 19 1/2"
At idle in gear (750RPM) with the dizzy on ported vac, I'm running 15 - 15 1/2". With the needle resting more on 15".

At idle (1000RPM) with the dizzy on manifold vac, I'm running 19 3/4 - 20"
At idle in gear (750RPM) with the dizzy on manifold vac, I'm running 16 - 16 1/2". With the needle resting more on 16".

Is this good for a freshly rebuilt ZZ4? One thing I noticed when changing from ported to manifold vacuum, the idle increased to 1300RPM. I had to lower it to a grand to get a better comparison. Whats the reason for this? Does this affect driveability?

While ported, the truck idles very well. Matter of fact, a buddy of mine has a '03 vette and its very similar.

With manifold, it seems to be more choppy. Hmm