hey guys, I have a really puzzling problem.

the injector in cylinder 2 is staying wide open all the time, I have replaced the ecu, distributor, injectors.. etc etc. and still have the same problem. But when i change the wiring from injector 2 to 3, 3 will stay open all the time. so ive narrowed the problem to be the harness, but how can i tell if it is the main harness or engine harness? any kind of tests i can run? i dont wanna go waste 200 or more for a engine harness, and then the problem lie in the main harness!?!?!