I will try to be as brief as possible. 91 Silverado with 02 4.8 swap. After first several attempts to start, engine ran (each time I tried to crank it, took several tries. Low fuel pressue). Replaced fuel pump, upgraded fuel lines, filter, injectors. I would later discover bad head gasket. Rebuilt engine. Installed ls6 cam and had heads ported with larger valves (ls1 valves). Now the hard start is not as bad but it runs really rich. Throwing all sorts of codes. Multiple engine misfire, 02 sensors, knock sensor etc. (all those sensors are new) my nephew, whose a mechanic, scanned it and discovered cylinders 2 and 7 misfiring nearly constantly. We swapped the #2 and #4 coils to see if that was the problem, however 2 and 7 still had the worst misfires. He also discovered the fuel trim learn is disabled both long and short term. I know I need to add another ground, but could the fuel trim being disabled explain the hard start, running rich and misfires. Btw fuel pressure is 50psi once ignition is turned. Thanks in advance for any help.