I wouldn't think they would not need to mess with the linkage, but you never know. Trace the linkage through all it's connections and make sure none are loose, make sure the pump lever is moving full stroke with the foot feed depressed to the floor. I bought a 240D with the problems you described and thought the motor was shot. Turns out a gommet had fell out of the linkage at the top of the engine and the pump was not opening up all the way. The mechanic could have unknowingly destroyed a bushing or grommet that was already in bad shape from age.