I'm not sure that the Renolds # is applicable to a Gas [Air] only
applies to Fluids for determining whether you have Laminar or Turbulant
Flow for Thermodynamic Calculations.

Surely once you have a Vacuum the Pipe/Tube is empty so you are Sucking
Nothing other than any Air that Leaks in? Therefore Pipe Size/System
Volume is probably best kept to a minimum?