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Normal compression for a good cylinder, tested with all spark plugs removed should be about 175psi.
Sometimes results will vary depending on the testing method and gauge so test all cylinders and see if they are the same. That is more important than a single cylinder result. In other words if all cylinders are reading 160 then that should be fine because we would think the issue is in the testing equipment, BUT if you have a 155 and the rest are at 180 then we have a cylinder issue.