Fuel Pressure vs Vacuum on 6.0

[r6z4o6]

Both of those codes( P01X4) could be caused by running lean, or even as simple as vacuum leaks. How long have they been on, that is pointing to both front sensors. The last code sounds like you need to inspect your rear knock sensor under your intake in the valley tray. Prolly rusted. I wonder if you left out the dysfunctional rubber knock sensor plug, would it allow water to simply evaporate? Since it obviously can't keep it out.....

[HarleyDave]

Had the O2 codes since the install, really haven't driven it much. So those could be in the wiring I guess, the harness came with the eng. As for the knock sensor I did have a coolant leak but fixed it as soon as I found it so I need to pull the intake and check it out. I think there is a thread for checking it on here. Don't think that I have any vacuum leaks but will double check for that also. So running lean can cause those codes as well?