’05 V-8 - "low humming tone"?

Another note about my '05 v-8 Sport Ed. 4Runner.  At speeds around 70MPH +, I have an audible, "low tone drumming" sound.  Sort of a "whu-whu-whu-whu-whu"...(nice eh?).  It is only on accelleration...not tire noise.  It is very rhythmic and does not increase at that speed, just steady but gets slightly (barely) louder if I get on it above 80MPH...still same "pace", just louder.  Again, if I take my foot OFF of the accelerator (which I should do more of), and 'coast' at these speeds...no sound.  Ideas?  Thanks!

are you sure it isnt an exhaustr tone, and youre just not used to the vehicle yet? i have a friend with a 04 with the V8 and the exhaust has a nice sound to it..perhaps thats it?

Yeah, at first I thought it was likely exhaust intake or flow-through the system, but it's definately not something that you'd expect to hear...very noticeable but not obnoxious...it's odd...and does sound like a "powerplant" or something...hard to describe of cousre.  Thanks!