I just bought a 1996 gt 4.6 good shape body but need mechanical work which I thought was going to be easy. I did all the brakes brake lines master cylinder power steering pump and rack. Get it running pretty good with a slight misfire. Check the codes and I get a ton. Bank 1 rich bank 1 lean cyln 6 misfire.I noticed old owner changed out gas tank and left old fuel filter so I changed it finding the gas lines were a mess. The return was bent in half closing off the flow. I fix that mess and the rich code went away. I cleaned the mass air flow sensor and the lean code went away. Only thing left was the p0306 cyln 6 misfire. I changed all plugs and wires didn't go away. Swapped coils in front to see if the cylinder code would change and it didn't. I put in a new fuel injector in 6 fire it up and now Ive got a p0300. Multiple misfire. Now I am at a loss.