Revving up with additional air in neutral is normal.
There are other reasons a wideband may give misleading AFR besides the program or electrics. Anything that results in a different amount of O2 in the exhaust can fool it. Misfires, or burns that don't combust and progress completely at the temperatures expected. I'll post some links later.
It's very good that you are paying attention to rpm, vac and how it sounds.
"On a cam like that, vacuum goes up when opening throttle from closed. The greater pressure difference, the more flow, up to around 14"Hg when it chokes."
Sorry, don't understand that. What chokes?
[edit: corrected]
I got that backwards. The air mass moving past the throttle plates is choked at high vacuum. So when on the idle circuit at any given throttle position with manifold vacuum over 14.8 psi, the amount of air will be limited.
At 0.528 absolute pressure difference, the mass flow of the air can not be pushed any faster.
Whenever the manifold vacuum is below 14.8", changing the manifold vacuum will result in a change in mass flow of the air. This makes the idle to off-idle a little trickier with a hot cam because than with a stock engine that idles with high vacuum.
Below is a snip from Bruce "Shrinker" Robertson
It's a little bit of an aside but maybe you'll find it interesting.
11-25-2011, 09:51 PM
Location: Adelaide South Australia
As you increase the depression the air flow velocity through hole increases but only to a point. Once the gas flow velocity reaches sonic conditions the mass flow will not increase. You can suck on it as hard as you like you wont get anymore air through the hole. The only way to increase the mass flow through a choked orifice is to increase the upstream density(eg blowthough supercharging).
For standard atmospheric conditions when carby tuning (in practice) that occurs at around 14.5 to 15". Correctly said choke is reached when the downstream absolute pressure is .528 of the upstream absolute pressure. The air passing the throttle blades may be in Choke, but the air in the Tslot drilling may not be because there is an air bleed reducing the pressure in the drilling. There is the problem.[...]Additionally liquid orifices have vastly different choke point ratios because the speed of sound is much higher[.] So although the air is choked the jet isnt. Funny isnt it.
