Is your fuel filter okay ?

m103 midrange hesitation
 

My 1989 190e2.6 encounters some hesitation from 2000-3000rpm when I floor the pedal and keep it there. At this time, you can feel the engine hesitate and surge, as if I was stabbing at the gas pedal.

Above 3000rpm, it goes back to normal, as if the throttle suddenly opened to full open position. My car has a manual transmission, so I can feel the engine as it goes through this sequence of events.

It seems that there is some sticking valve or other mechanism in the throttle body area.

Is it also possible that there is a leaky vacuum line somewhere in that area?

anyone familiar with this symptom? thanks in advance.