After tire balancing, alignment, new shocks,mounts,.ball joint,control arm bushings, I took the advise of forum member RJ237 and had the tires rebalanced using the Hunter Road Force machine. For $100- problem solved! Thank you all for your input.

 

Many of us have learned over the years that Hunter Road Force Balancing is essential for the XK8/XKR. My local Discount Tire store manager knows that whenever I bring my wife's 2006 XK8 to him (for new rubber, tire repair, wheel damage check, or whatever reason), I expect a fresh spin for all four wheels on his Hunter unit at no charge before I leave his store....

 

I had nearly the same issue of front end shimmy / vibration several months ago even after 2 rounds of conventional spin balancing by different shops. The Road Force Balancing is necessary to correctly balance as well as to determine if there is internal structural damage to the tire. 2 new front tires later and all is well.