i have a 98.5 cummins 3500, it has been acting up by having low power, sputtering and having a dead pedal when i stomp on it, check engine light comes on and sometimes it will completely die. no codes come up and my TPS and fuel filter have recently been changed. I have no clue what it could be but i am leaning towards injection pump but would like to know if anyone knows for sure before buying one. thanks