I have a 2001 Cummins with 330k miles 6 speed and a superchip tuner and which I believe there stock injectors but cant be sure since it smokes like a damn train, but well the other day I noticed a slight change in the sound of the motor, but once it idled for a bit it cleared up. Well, driving home the day later since it was warmer I decided to be a little hard on it for a mile or so, well, I noticed at 2500 rpm in sixth gear everything sounded fine but it wasn't till I went and let it idle I noticed an awful miss in it but after ten seconds or so it went away. I had a few people tell me it could be an injector, others say IP and some say fuel leak/low fuel pressure. What could cause this?

 

Bad vp or bad injector(s)