see attached
that TSB shows an impressive amount of work they are willing to to through to "reduce" steering flutter. yikes.
one of the above mentioned Tacoma, and obviously this TSB regards LX460's. My 4th gen T4R has similar 'phantom' vibe that moves around, goes away, returns, in a seeming random pattern, but always at speeds of about 65 to 80.
RE-balance of tires will change the pattern a little, but it never goes away. To me, paying way too much attention to the issue over the same roads at same speeds at same times of day with same [approx] 'warm-up' time, it seems like a "sympathetic vibration" being produced - a harmonic maybe involving the driveshaft, tires, wheels, steering rack, linkage to steering wheel.
A question for you who suffer; do you notice the same vibe affecting the floor of the vehicle, as though it were emanating from the rear wheels? if you watch the back of the passenger front seat its a pretty good gauge... you'll see it vibrating at the top.
I notice the vibe also is much affected by the road surface. Seems that when it gets 'aggravated' it will continue for a long ways until the road changes or I stop for a snack or something, then it may disappear for awhile.