I can't put a finger on just where the sound is coming from, it is alnost all around me. It is not related to RPM, the problem only rears its ugly head at speed. I don't have any abnormal feel in the steering wheel. It is felt more in the seat of the pants and is quite "loud", it is actually hard on the ears at about 57 mph. It is not any sort of metal sound. I have had many a car with out of balance wheels, it just doesn't feel like that and I have not heard a harmonic sound with that problem before, but of course i could be wrong. I will have all 4 wheels rebalanced. I like the idea of getting the rear wheels up and testing but safety feels like an issue. On the commment of unis, what are you reffering to?