Uniformity of compression pressure between cylinders is far more important than the actual pressure number. I've seen pressure figures on the same cylinder tested with four different gauges show as much as a 15 PSI difference in readings. All the cylinders should test within 10% or less of each other- - - - -5% is better. If you've got a minimum reading of 80-90 PSI, that's plenty of compression for smooth running and adequate power. I've seen engine that ran smoothly and had acceptable power with compression pressures as low as 65-70 PSI, but gauge accuracy becomes more of a factor with the lower readings. Plugging a compression gauge into a shop air line with a known pressure reading is a good way to spot-check the gauge for accuracy.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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