Did you ever find a solution to the problem? My 07 is250 has the same issue with the humming.

 

Which one? There are several questions and topics in this discussion.

My BFG G-Force Comp 2 A/S are great tires for speed, traction, and wear but they come with 2 complaints.
1) very noisy, and double that as tread wears towards replacement.
2) when parked hot and driven on a cool day (next day) they take a set and vibrate for about 3 highway miles and it goes away. Again, age related. New it wasn't a issue.

I'm moving on to something else...

 

Yes, it turned out to be tire noise. The tires on my IS250 were worn on the inside causing a noise that sounded like it was coming from the differential. I put new tires on and the noise was gone.

 

If your tires are wearing on the inside and not even across the tread you need to check out this thread.

https://www.clublexus.com/forums/is-...-bushings.html