I have an 03 that had the droning problem. The dealer fixed it with a well known service bul. If I remember correctly it involves a different skid plate, steering dampner, and new lower control arms? They told me it was a harmonic problemin the front drive train. I always thought it felt like a harmonic problem around the intake(throttle position sensitive). I do know that the steering "feels" alot tighter at slow speeds than before.
I hope this helps.