GM-GMC: misfiring, mechanical problem, problem thanks

Question
i keep getting #5 misfire. have changed plugs, wires, cap & rotor, and #5 injector.  what else could be problem???

thanks

Answer
My specialty is diesels, but I will try to help.
If the parts you installed are good, about the only thing that is left is wiring damage that keeps the injector from opening correctly or a mechanical fault in the cylinder.
The mechanical problem could be a valve not seating or rings that are not providing enough compression for the cylinder to fire.
A gas engine needs air, fuel, and correctly timed spark and compression to work properly.  Check each of those items out until you find out which one is causing the problem.