Vacuum powered sap piston pump

[pdr]

Has anyone used a vacuum powered sap piston pump? (pg. 50 of the 2012 catalog) Does it work well?

[cavanmaple]

a friend has one, finds it steals 2" of vacuum regardless the size of pump. I belive they do work well, but is it worth the vacuum sacriice to run the piston pump if running high vac?