It sounds like my intermittent bog down on acceleration problem.
I am still searching for the cause. I have posted a couple of times, but no response. The bog down is accompanied by a fixed duty cycle of 93% (which by the way, is not in the manual). The closest is 95% (deceleration shut off switch).
I am pretty sure it is an electrical problem (in my case).
Yours sound awfully familiar to mine.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
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