My 94/2.2L exhibits this beginning at 90Kmh and woesening to a shaking on up the speedo. Just added new front tires jic and it's still there. The shimmy periods run about 3 secs apart for 2 secs or so. Suggestions on where to begin t-shooting are welcome. Unusual tire wear is present with cupping of the threads.
Thanks/Merci

You have a toe in problem and/or needs new struts.