@crashD
it's an early model which has had the contrasting (grey) bumpers painted to match the car, the lights and grille have been changed to make it look like a late model 600 as well and those rims were fit later. early model 300SE's and SEL's had patheticly weak engines, they had no bottom end torque for that heavy weight. the later 320 models are the more desirable ones.
honestly this is something i would also do to my car if i had a W140 but for some reason since there are no interior and engine pics i'm guessing it is pretty worn out inside and hte engine is weak.