I tend to have a miss or hiccup in my 1990 300CE. I have replaced the ignition wires, rotor, distributor, plugs. Fixed vacuum leaks.
It tends to have more when the weather is hot, than when it is colder outside. I also replaced the fuel distributor. There was some improvement but did not fix the problem. Also, I use only super unleaded fuel.
One mechanic had fixed this problem, where he replaced all the spark plug boots with older style VW boots, which are all plastic, I think these did not have any resistance values. The car ran sate mooth for a year.
Unfortunately, this mechanic retired and moved.
He had kept the car for like 1 week to fix this hesitation issue.
When I tried to remove these VW spark plug boots, they broke.
So, I replaced the ignition wires with factory set.
I have also noticed that if I accelerate slowly, it tends to miss less.
The spark plugs are not wet. I also tried Bosch vs. NGK (regular not platinum) NGK tends to have less miss.
Any ideas??