Injection Pump Failure?

I have a 2001 Dodge Cummins H.O. with the 6 speed. And I first bought an Airdog Lift pump to try an save my injection pump then the injection pump went out. then bought a new injection pump and it was running for a couple of months then i changed a fuel filter and then it happened again same problems. It sputters, blows white smoke, barely any power i cant even drive down the road, fuel starvation. and my chip shows the code P0216 and P1693. Same problems before i bought the pump. then when i put the IP in i put 100 hp injectors in. Then i did some trouble shooting thinking it was the lift pump so i had them send me a new lift pump and same problems. should i send the injection pump in to get fixed? i think it could also be a plugged up injector or the throttle position sensor but everyone iv talked to agrees that its just probably a crappy IP out of the box, a warn seal or somethen. It would maintain a fuel pressure of about 7 when it usually is 11-15 psi. Any suggestions on what it might be?