I have a 98 Buick Regal GS with a shimmy at speeds of 65+ under load, when i let off the gas the shimmy goes away, get back on and its there. I have had the tires balanced, alignment done, new end links, tune up done recently and cannot find the problem. Thanks for your time and assistance in helping me out.

Check lower ball joints and control arms. Another possible scenario is are the CV joints.