Looks like the throttle actuator to me.
The knock sensor doesn't retard the timing. It gives a generated voltage signal looking much like a graphical expression of noise to the engine management system. Based upon the controllers program levels of noise are reguarded as knock and the cylinder at fault (the system can tell which cylinder through calculation and the fact that there are two sensors). The management system then reduces timing after an event by 3 degrees. If after the next firing a similar judgement is found, another 3 degrees are removed. This goes on up to 15 degrees per cylinder, individually. If after a firing it is judged that there was not a knock then a degree of timing is replaced. Thus 15 degrees are removed in a possible 5 firing events but takes 15 firings without knock to return. This is dynamic and ongoing.
Bosch Master, ASE Master, L1
33 years MB technician