Personally, I love fuel injection, when working they are great under different weather conditions.....anyway, I think this is D-Jetronic sytem (like my Opel!), check for a potentiometer on the end of the throttle cable which measures throttle position (you need to get some manuals here).

If it were dirty or corroded, then it may have some open spots, and when you operate it rapidly (pumping the gas pedal) it clears the corroion or simply slides to a slightly differnt spot..