Mighty fine looking laboratory you have there Art! Though I can't quite seem to make out that brand of Yankee beer, I see it's in a red and white can and that's good enough for me (says he who would have been well served by buying stock in the Old Milwaukee brewery...)

"I wonder, given that the Regina, using intake air temp and manifold pressure, does not need to meter the air used by the idle bypass, whether that extends or reduces that range over the Bosch system."

Not that I'm beginning to obsess over IAC valves or anything... but here are my uneducated thoughts on what might prove to be a proper comparison of range attributes between Bosch and VDO valves:

Some scanners have the capacity to display an IAC pulse count (I don't happen to own one) - the higher the count, the more air is bypassed and hence, higher the idle.(Please humor me, I know I'm preaching to the choir -) It seemes to me that with said scanner and a vacuum gauge one could say, start with a Bosch sensor on a Bosch car, idle, record IAC count and vacuum gauge reading. Then introduce a slight vacuum leak, again recording IAC pulse count and vacuum reading. Continue to introduce progressively worse vacuum leaks / recording data untill you feel "enough is enough" (and beginning to worry about the amount of gas in your oil!).

Have an Old Yankee Milwaukee.

Now, repair all self induced vacuum leaks, put the car in gear and record IAC count and vacuum reading. Put a slight load on the engine while in gear (this is why I recommended the beer previously) and record IAC and vacuum readings.

Install Regina valve into the same Bosch car and do it all over again.

Compare results and have another Old Yankee Milwaukee - you've earned them both, regardless of whether the test results amount to anything noteworthy.