There's some very informative info here..
So, most of the gauges out there are 2 to 3 PSI off and usually on the low end.. For instance, my "Digital" Gauge reads 30 PSI and the Schrader Master Gauge reads 33 PSI. The only gauge I would trust is the "PCL". The TPMS are surprisingly accurate within .5 PSI of the Master gauge. That's said my GS 350 sweet spot is a bit over 32 PSI (32.3) according to the TPMS, the PSI recommendation is 33 PSI. This is cold tires that have sat overnight.