Since fitting my TRD rims last summer, I've never been able to drive the car without having steering wheel shimmy at 60+ mph, even after getting them balanced. It's blooming annoying!
I am taking the GS here
http://www.vibrationfree.co.uk/index.html
to get the wheels dynamically balanced - that means they do it on the car..
They already did another Lexus last week, and cured his issues, so fingers crossed..
Will update you later in the week, as I'm going on Wed evening.