I did some testing with my own test gear with a number of different gauges.
Autogauge and a couple of other "Supercheap specials" had errors.
Autometer, VDO, somne old school Trust, HKS maunal gauges were spot on.
I did a couple of Defi boost/oil gauges and one eletronic GReedy (all I had access to) One Defi had an error around the 15psi (was about .5 psi out) but others all good.
The Autometer Liquid filled gauges are the best manual ones, Any Bling Bling ones like Defi are good to.