Fellow mass spectrometerists, check this out. I'm running some calibration standards and all the sudden, from the 100ppb to the 200ppb, internal standard recovery changes from 100% to 80%. Naturally thought it was sample introduction; checked for clogs, changed cones, changed to new nebuliser, still same drift, sometimes after 5 cups. Then it eventually, 5 cups or so, it kind of creeps back up around 100%.
Today, I was looking at the real time display, in deep thought while I watched the 115In and 209Bi signal intertwine bouncing across the 20 in. flat screen when I figured it out. I accessed the accessory window and switched the peristaltic pump into rabbit mode. Sure enough, the signal drops, probably around 80%, but just going off counts per second at the time. Let it equilibrate and switch it back to regular pump speed, 24%. Oh, man, took like 3 or 4 minutes for the counts to get back up to where they were before rabbit pump.
Edited ACL script, no rabbit pump, calibrated fine, loaded samples, got to name a new type of drift: Rabbit Pump Drift.
I also named Seesaw Drift, this is when the low mass internal standards drift up while the high mass internal standards drift down, or the other way around.
 This is what the software that runs the ICPMS calls max speed pumping. Good for washing the probe during rinse.