I agree

Always do a flow test when doing a pressure test..specially where the complaint/condition is at a a time-frame when high fuel consumption is demanded. [ Like WOT or heavy engine load condition]

A quicky in-situ drive test is to drive up a decent graded hill with max load on the engine w/o downshifting..low volume will show up quickly under those conditions...[ as will weak plugs/ign]
A 'T' in a pressure gauge will get you volume and a trick is to use a clear line on the flow test b/c you can then see any air in the line as you do the flow test. The old benz gauges actually had a glass tube as part of the gauge so the Tech could monitor for possible suction side air when doing a flow test.
I just put a loop in the clear line and if there is any air , it shows right up..
Then yu check lines and clamps, specially pre-pump.

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A Dalton