Aerated fuel, Ingection pump, waste gate, codes P1214 P1656

My Truck:
1996 Chevy 3500 HD, 6.5 turbo diesel, manual trans

Some history:
For the last 2-3 years, lots of black smoke exits the tailpipe when I

were you able to check the timing of your injection pump with a scan tool, setting the injection timing can be very difficult on these 6.5's the injection pumps also have stepper motors on them that can advance and retard timing so maybe the stepper motor is bad or stuck and making the timing off and causing it to smoke and have little power. you could try tapping the stepper motor lightly to see if it makes a difference.. just something to consider before spending lots of cash . good luck