I have just came across an amercian company called level 10
who do a complete kit to uprate the supra auto box
www.levelten.com/store/toyota.htm
the way they put is
PTS Seal, Gaskets, Washers, Bushings, And Rings
Detailed Performance Instruction Sheet Included
Includes Necessary Parts To Modify Pump, Valve Body, And Internal Factory Deficiencies
as far as i can tell it should leave your supra autobox to the same spec as a boost logic one but for a lot less money
the kit is i $998
could be worth a try if the bloody exchange rate wasnt away to hell
about £750 plus p&p