this is a problem with a 1990 300 SEL, 145,000 km.
Car sat for over a year inside. It was given a tune-up: new plugs, cap/rotor
and button and wires. Car worked perfectly for about 2 weeks the gradually lost power and acceleration.
Fuel filter was pulled, was full of brown gas (rust?)
new filter installed,
lines blown out with compressed air,
tank strainer cleaned. No change/very little change.
Filter at fuel distributor checked,(OK)
All injectors checked (OK)
Cold start injector checked (OK)
Fuel pressure over 100 lbs.
EHA valve swapped with one from a car with same engine.
Still no change( will work a bit better if it sits for awhile for a short time)
Now we are helpless!