Hello, I am having issues with my truck and I need help. I have a 1999 GMC Sonoma and it is misfiring bad. I was reduced to a part swapper and spent loads of $$ like an idiot to no avail. The truck has new spark plugs & wires, new injectors, injector harness and fuel filter, and I also put on a new valve cover & intake gasket just because they were off and who knows how long its been since they were changed if at all. The truck is still having the same issues and I'm back at square one with no progress to show for it. I need guidance on how to go about fixing this truck before I dump more money into it. I understand the P0200 is most definitely causing the P0300 code, so I need to isolate why how I have an open injector circuit. I really need my truck fixed because my poor WS6 has 223k miles on it and doesn't need to be my daily any longer. Please help.