I have a 2002 Cadillac DeVille, I ran a diagnostic on the car and it was running these codes, P0202, P0203, P0208, and P0300, I was figuring maybe dirty injectors so I pulled the injectors and sprayed them out with injector cleaner, then I cleared the codes and now I am getting codes P0203, P0208, and P0300, I then was still thinking injector problem and I pulled injector 3 and swapped it with 1 and swapped 8 with 6, cleared the codes and started the car and let it run, the codes remained the same, what could be the problem?