Mercedes-Benz W126 clogged and leaking fuel injectors

Yes. During long storage fuel can turn to resin in the fuel injectors, so they clog and the engine runs poorly, especially when cold. Replacing the injectors has clearly improved starting.

A leaking injector does not hold the fuel line pressure after shutdown, and petrol runs into the cylinder prematurely. The result is difficult cold starting and reduced power. A leak can be checked by leaving the injectors under pressure overnight.

The injectors are either cleaned (for example ultrasonic cleaning) or replaced with new ones. If one injector is faulty, it enriches the whole intake manifold, so replacing all the injectors at once often makes sense.