You have the same problem with my 96 LS400. I took it to my friends transmission shop and found the rear transmission mount is gone bad. The mount is on order so I can't say if this will solve the problem. But before you run out and buy new tires I noticed you mentioned reving the engine while the car is in parked, have you tried that yet? If not try it, leave the car in parked and run the RPMS up to about 2K to 2.5 RPMS, listen and see does it hollow sound comes and goes. If it does it's not your tires or your rear end since your car is not moving. It has to be related to mounts or something like that. I hope this helps. Once I get my motor mount installed I will post the fix.
Brad
Problem solved!!
Reverbitation, hormonic sound. It turned out to be the rear transmission mount. I purchased the mount form discounttoyotaparts.com, for about $44.00. My partner put it on. It not only solved the hormonic vibrations but also greatly inproved the shifting of the transmission, everything feels realy solid not - no jerking around or weard feeling down shifts. In order to check the mount the transmission must be pushed up on with a lift of some sort. The bount is rubber, so if you see it seperating it needs to be replaced.
Brad