I just bought my 93 Gm 3500 with 6.5 TD. The injectors sometimes sound so loud under load that it bothers me to the point that I back off the throttle till it goes away. It does it warm or cold. The guy I bought it from says its always done that as long as he's owned it, about 5 years. Any suggestions would be greatly appreciated. Doug

Cold advance solenoid might be getting energized when its not supposed to.

Unplug the back wire on the injection pump top cover and see if that fixes it, if it does, then you need a new coolant switch that operates the solenoid.

Check the injector lines where they come through the lower intake maifold and over the valve covers for missing mounting clamps, if the lines contact anything but the injector they can be a nasty source of noise. Also if the cold advance solenoid is the problem, remember there are two temp switches one on the coolant crossover manifold and one on the drivers side head.

Good point MDT.

The one on the crossover is the switch that operates the cold advance/cold fast idle solenoids. Two heavy gauge wires.

The one on the head is the sensor for the temp indicator on the dash. Single light wire.

Thanks for the help, Doug