The vacuum readings were wrong. Tested today with another guage and here is the results:
@ 1,000 rpm 12 deg adv in park its showing a slightly bouncing 14 to 15" vac.
@ 700 rpm in drive with foot on brake its showing a slightly bouncing 10 to 11" vac.
On both test the guage will occasionally drop 2 or 3 numbers then come back to where it was at.
The off idle fluttering stumble is still there. Now if I slowly bring the engine up to 2,000 rpm then nail the peddle to the floor there is no flutter or stumble. It accelerates fast and sounds good. When I nail the peddle I notice the vacuum guage drops to "0" then jumps fast and smoothly up the scale.
With the above vacuum readings what power valve should I be running?