Another suggestion, see if there is an electronics or instrument shop near you and get your analogue gauge tested for accuracy. It would rule that out if it's accurate. Once you do this, the OBD2 will allow you to compare the measurements between digital and analogue. Remember though your feed for the analogue gauge is from a different source.
Remember also though, 21psi boost isn't likely to be a big problem because you're not likely to be at full boost very often and not for very long so it's really a moot point unless you thrash your Hilux regularly
The problem becomes dangerous if you lug the engine at low revs and high boost settings. That's not very likely because the engine needs revs to make full boost. Use your gears to keep the revs up. The sweet spot is around 2500-3500 revs. Making your engine lug at lower revs damages all sorts of components not just the turbo. They love to spin because that's what they're designed to do.
Cheers Gipsy
although I'm sure somebody will challenge that
even Einstein wasn't certain of his theories.
My 2013 auto D4D DC SR5, prefilter, 3" exhaust and Chip with egt probe, stock SR5 rims with Toyo Open Country AT2 265/65R/17's