Hi, guys. I have a 1992 Legacy, front wheel drive only. It has recently started to get a rhythmic, fast "duh duh duh duh duh duh" (if you can imagine that) when the car gets to about 40mph and above. It's coming from the the front passenger side and it stops when I take my foot off the gas pedal. It makes the car shake very very little, if at all, but the sound its making is very apparent. I had new tires put on a month or so ago, so I know they are balanced and aligned. I'm wondering what could be causing that.

I'd guess a bad half axle or a worn out wheel bearing. Bad ball joints, bad tie rod ends, and worn bushings can cause vibrations as well, so you may want to check over the whole front end to make sure nothing is loose.