I recently bought a 01 7.3 with 230000 miles. The previous owner sold it because he had an issue with it, and I can't figure it out either. When accelerating the check engine light comes on,and it does not start when warm. Testing showed warm cranking was only building 250-300 psi on the HPOP. Previous owner replaced ICP, IPR, and Cam sensor. I replaced injector O rings, and HPOP with a T-500. Issue still is there. Any thoughts? I'm out of ideas. Compression test showed 400-425 on 7, and 360 on 1. Also when letting off the throttle at low speeds sometimes it will die, and it seems underpowered. So all in all it still has a low HPOP pressure even though it has new orings and HPOP.