You need a shop that has an exhaust analyser, pressure gauges to check the fuel line pressure and residual pressure. - do not try to adjust the fuel distributor without the analyser otherwise you will be shooting in the dark.
The K-Jetronic system is quite simple but can become really a PITA if you dont have any tool to actually "see" whats happening. Ask for this Haji sb, and if he does not have the basic pressure gauge setup - look for someone who has.
I am writing this because I have seen many K-Jetronic car owners in Karachi Pakistan suffer from excessive repair bills because "famous" mechanics were shooting parts at the car trying to fix it. Anyone with a set of torx and hex bits is not a benz mechanic.