my brother has a mercedes diesel, i believe late 80's, and it has severe power issues. it will barely idle and has no power what so ever when you push the skinny pedal...however after a while of no power the turbo starts getting fueled and it runs great....until it drops down to an idle again. he has put new injectors in it, new air filter, and fuel filter. any ideas?

 

Drain the fuel tank and clean the tank strainer. Also make sure no air is flowing through the primary fuel filter.