Rule 66 C:
The following devices are not considered pneumatic devices and are not subject to pneumatic rules (though they must satisfy all other rules):
A. a device that creates a vacuum
B. closed-loop COTS pneumatic (gas) shocks
C. air-filled (pneumatic) wheels
I assume the "must satisfy all other rules" clause means you can't use an electric vacuum pump unless you power it with a legal motor.
We experimented with a large Piab venturi vacuum generator. That worked well, but it's specs state it requires 3.8 CFM (cubic feet per minute) of air flow. The FRC-legal compressor only puts out .88 CFM.
We found a much smaller Festo venturi (#547707) that also did the job, but still requires 1.8 CFM; about 2X the compressor's output.
If we use it we'll need to install quite a few air tanks and pressurise them in the pit before each match. We'll also figure out a way to run the venturi only when needed and not a second longer.