Hi,
I have a UK GS300 MkI fitted with the Sport Option 8.5" Front and 10" Rears. I've tried to establish the recommend pressure for these and it's not easy. Lexus, if you can get them to commit to an answer just go with that shown on the door sticker for the standard 16" option which is 35 psi front and 36 psi rear. Although a lot of UK drivers report centre wear on the rears which would indicates 36 is too high. Other UK drivers seems to do OK with 32 psi all round. I think it's a case of take your pick and monitor the tyre wear.
If you do get a definative answer please let me know.
By-the-way the Supra is amazing , always wanted one but with a family the GS was a compromise.