I had a similar problem, a noise and vibration under light throttle while in
high gear. It was a few years ago while my '97 was still under warranty so
I don't remember every detail. I could hear and feel it from the driver's
seat, but it was not too bad. It was much worse sitting in the midcabin
seats. The AWD cars have two shafts supported by a bearing. The shaft, I
think the forward one and the bearing were bad. They were replaced under
warranty. If you are not under warranty I would live with it or be prepared
to part with your wallet.