Did you check an alignment on dealers machine?
Strange thing I found when i was using Michelin Latitude.... when you start driving and tire is temperature is ambient ( around 32 psi), so after 20-30 minutes of driving , espessially in summer time( like 75-85- degrees), tire pressure rises to 35-37 psi on Michelins and in that case you are driving on overinflated tire... usual temperature gap should be 2-3 max. of cause it depends on tire...
It does not happening to my Vredestien's... gap on VR's is 2 psi, regardless of outside temperature