Car runs great, except for one little quirk. While driving at highway speeds, 60-70mph, if I let off the excelerator there is a quick jerk that scares the heck out of the passenger. (I know I'm letting my foot off the gas, but the passenger doesn't) I was told the problem may be in the drive train so had that all gone thru - twice - and still no dice. Problem still exists. Also checked the vaccum advance and it made no difference. Anyone else having this type of problem?