Thanks for the link, Normk; however . . . I missed the trigger coil air gap effect discussion in my first reading; gotta go back and read it again!
For programming the ignition map, looks like we need to take a look at this article:
To replace one of these units, you could adapt one of our previous designs, such as the High Energy Ignition (SILICON CHIP December 1995 and January 2006) or the Multi-Spark CDI (September 1997). Alternatively, you could consider using the Programmable Ignition System from March, April & May 2007.
The spark advance of the CDI on Kawasaki V-Twin ATVs (Prairie, Brute Force, etc.) is determined totally by engine rpm input (trigger coil impulse rate), electronically, without manifold vacuum input.
Aftermarket, wire-on modules ADVANCE the initial spark timing and allow the engine to stand the quads up on their hind legs (the factory configuration retarded the spark to prevent end-overs by enthusiastic but unfamiliar/unskilled riders, hoping to reduce vulnerability to product liability claims).
So . . . no reason NOT to incorporate manifold vacuum as an ignition timing input parameter (along with rpm and perhaps throttle position, etc.), but . . . not typically done with motorcycle/ATV CDIs today, AFAIK
. Spark timing is varied electronically with input only from trigger coil pulse frequency, seems to me.
Gotta find that, "Programmable Ignition System" article from March, April & May 2007!