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[Takummie]

I recently had to get my rear tires changed but I couldn't get a pair of 255/30R19 for numerous reasons so I slapped on a pair of FALKEN AZENIS FK510 275/30R19 96Y XL. The tires say max load 710KG and max pressure 340KPa on the side walls. The speedometer is well within tolerance (actually became more accturate) and it gives very nice ride, all seems fine, but I'm very confused regarding the tire pressure.

My door sticker and owner's manual says:
For front 225/35R19 88Y XL, 270KPa for up to 2 passengers or under 160km/h, 290KPa for above
For rear 255/30R19 91Y XL, 320KPa for up to 2 passengers or under 160km/h, 340KPa for above.

Now my front tires are within OE spec but rears are changed to 275/30R19 96Y XL. 340KPa for a LI of 96 is within max tolerance but seems crazy high. I did a little research and I guess I should make their max load capacity match OE spec but I can't find any information on that over 290KPa.
From this chart I figured LI 91 and 96 comes to around the same max load capacity with a pressure difference of 40KPa. Does that mean I should follow this pattern and put 300KPa in my new tires? Or I should follow my old tires' max load capacity of 615KG and put in around 250KPa? Or totally disregard and stick to 340KPa? I'm really not sure. I'm currently running on 270KPa/320KPa for now.
Any ideas?