we got a used 79 300sd turbo diesel and it was in great condition other then the driver door inside handle. but anywas it seems that the turbo goes on and off cuz sometimes when were on the high way well hit the pedal and the car just takes off other times its like were barely pressing a little more. any help would be appreciated

This engine uses a overboost control circuit that can be the culprit. A clear plastic line that goes from the intake manifold to the injection pump must be free of restriction. This includes the hollow bolt that connects to the intake as well as the boost control solenoid. These circuits often get gummed up with the carbon from the EGR or blow-by debris. It is also possible that the switch on the intake that controls the overboost solenoid is the problem. Bypass the boost control temporarly with a piece of hose and see if this helps.
Good Hunting!