The techs at Sanderson Ford in Phoenix discovered the cause and possible fix for this problem on Chip's car. The very day I was at Multimatic they had just figured it out. My car was already down the line so it did not get the fix. The knocking started in the spring on the driver's side. I let the local GT service dealer know what it was and took it in for the fix. Like AJB said, the torsion bar on the drivers side had to be loosened , a spacer put in and then re-torqued to a different number. The tech was very cautious and ended up doing the adjustment 3 times talking to Multimatic every time. They had the car about 10 days but it worked perfectly and I have had no repeat in 5 years and 10,000 miles. Chip posted it here on the Forum someplace because I remember him commenting on how Peggy complained about a knocking he couldn't hear. It is a pretty easy fix. I was at Multimatic the beginning of August, 2018 and my VIN is J169. Car was delivered at the beginning of September, 2018 to give you a time frame. I hope this helps. Too bad you can't come. I will make up a bunch of ugly stories about you to keep people amused.