I have done top end rebuild of this engine due to sludge build up. Rebuilt junk yard heads, New timing chain, New Gaskets. New Cam Followers. Lots and Lots of cleaning. After putting back together, would not start. Replaced Fuel pump and it fired up. However not running on 4 and 6 based on spark plug unplug test. Fired a code after running a few minutes. DPFE sensor high input, and fuel system 1 CL fault. My numbering of cylinders is front Left to Right, 4,5,6. I have performed the following tests with results of no difference. Sprayed flammable brake cleaner all over motor, no indication of vacuum leak. Swapped coils, from 4 to 5 and 6 to 5. Removed lower manifold and inspected for gasket issue, cleaned head surface a little more to ensure seal. While upper manifold was off I disconnected all plug coils and had engine cranked over, all cylinders injectors were firing similar spray pattern. Also removed plugs on 4-6 and performed compression test, all 175-190. Plug 4 showed no sign of combustion, 5 is normal, 6 shows some sign of combustion, but does not seem to change idle when coil is unplugged. Swapped plugs in 4 and 5. Checked all plugs in coils to verify each cylinder is firing. I dont see how I could have mixed up coil or injector wires as they are wire managed pretty tightly. I have not swapped injectors around to see if things move. I am fairly confident valve timing is good as 5 seems to run strong. I hope someone can h elp steer me in the right direction on this one.