I have an intermittent shake and shimmy in my 98 Forester (54K miles), especially at highway speeds. It is a thump thump shake when the throttle is on, and a side to side shimmy when we are off throttle. It gets pretty bad sometimes, especially at high speeds, but then goes away (while still at high speeds). Any ideas? It has nearly new tires on the front, and 3/4 worn on the back. The shake also occurs at lower speeds, though at any speed, it doesn't happen all the time. Thanks for any suggestions....
-Ian