Rear end wobbles back and forth at 66 mph or faster !!!!

freeway speed, rear axle, rear end, wobbles, rear, left, bearing, wheel, fixed, problem, back, freeway, week, posting, received, mechanics, street, emails, alignment, racing, off-road, years, failure, world, $175, w/labor, livelys, blow, diagnosed, successfully, national, city, cost, total, play, 66-80, started, speeds, months, wobbling, rim/axle, faster, 1991, excellent, runs, miles, 126k, pulls, nuts, tight

My 1991 N/A MR2 with 126k miles runs excellent. But a few months ago at freeway speeds (66-80 mph) the rear end started wobbling back and forth. It seems to come from the left rear rim/axle and only when on the freeway and pulls to the right. Other cars avoid me immediately because it looks like I am losing control of the car. When I am parked, there seems to be some play with the left rear rim. All lug nuts are tight. I have also used different rims/tires and I still have the problem. What