The most likely cause of low-power, when under load, in your Cummins N14 diesel engine is a lack of fuel. The problem can also be a lack of air flow.
Fuel or air.
This would be only caused by Excessive blow by from the engine position sensor.
Head gasket & oil cooler
Head gasket & oil cooler
Turning the fuel screw on a Cummins will determine the fuel flow tot he engine. If the screw is set too high of low then the engine will not run properly and could cause engine damage.
A very likely cause is a failed radiator fan.A very likely cause is a failed radiator fan.
The price of pineapples in Hawaii is less likely to cause an engine to hunt or surge.
Engine over full, diesel in the oil, excessive blowby.
Perhaps a bug on windshield.
most likely an intake gasket
It is the high temp and the high return Pressure inside the injector that causes the fuel To turn black
A few things can cause this problem, stuck open wastegate, excessive blow-by or an air leak on one of your intake hoses.