One thing to look at, specific to the 740, is the intake air hose.

The large rubber bellows type hose from air mass meter to throttle, can fold up when it gets fatigued and the rubber weakens. See if it has a natural fold or kink to it. What can happen is that it folds under high throttle conditions, but then is held in that position by engine vacuum... until you shut off the car, then if kind of straightens out. You might be able to catch it in the act if you do not shut the car off, and pop the hood when it happens.

In any case, new air hoses are only $15 or so.

Good luck with it, hope it turns out to be this simple.
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::: Rob Bareiss, New London CT ::: 92 244 M47 211K ::: 90 745GL M47 273K ::: 88 245DL AW70 190K ::: 84 242DL Project ::: 70 VW Bus ::: 70 VW Pickup Project ::: 71 VW Notchback :::