location of pneumatic components

R83 states the following:

Only the compressor, relief valve (P/N: 16-004-011), pressure switch, pressure vent plug, pressure gauge, storage tanks, tubing, pressure transducers, and connecting fittings may be in the high-pressure pneumatic circuit upstream from the regulator.

Does “may” mean “must” OR can the pressure vent plug be located on the operating pressure side? Does the relief valve have to be directly off the compressor outlet or would it be acceptable to have it on a storage tank on the HP side?

Anywhere on the high pressure side, is “upstream from the regulator”

Other rules govern locations of the vent plug and relief valve. See R87 and R89A. For those specific components, “may” does mean “must”.