Today, I isolated IP4 for 30 minutes or so and noted that it responded by decreasing from a nominal 2.6 mA @ 6e-8 torr to 0.6 mA (~1e-8 torr) while at 7000V,  This compares to IP12 (also isolated) which is showing 0.081 mA @ 1.5e-9 torr while at 7000V.  What's the point?  I'm glad I asked!  1.5e-9 torr is good enough for a new pump when pumping against on unbaked O-ring valve.