My 1999 A6 2.8 L 30V has developed an intermittent problem. I have just over 261,000 miles on the original engine. Other than service to cure oil leaks and other routine maintenance as required, most of the time the car runs fine. Lately if I run the car at highway speeds for even a little while, and then suddenly get off the throttle, like exiting from the interstate, the engine will start bucking and acting like it is misfiring. It will quit running unless I keep some pressure on the accelerator pedal. If it does die, it will restart. Sometimes a restart will cure the problem and sometimes it won't. If I park the car for just a few minutes and then restart it, the problem is gone that time. I am open to suggestions if someone else has had the same problem. (I am trying to keep this one going while I work on my 2004 A6 S-Line 2.7T that ate its alternator.)