my 97 has the 4 rear injectors stuck open when key is on and will fill the entire intake and throttle body if key is on causing a vapor lock. Please help

 

You either have the wires from the injectors to the ECM (computer) pinched and shorted to ground or a bad ECM. When you turn the key on the injectors get powered, and the ECM is supposed to control when they're grounded. Check your harness first.

 

Should the whole harness be check or is there a certain part that go bad?

 

Look for a break in the insulation. The "certain part" would be the computer. You could test that, maybe, by unplugging it and seeing if the flooding still happens. Or you can disconnect the injectors and check for a short circuit to ground with a meter. Many ways.

You might change your title also. It's misleading. Four injectors flooding might be a common 97 F150 problem. That would be a good title - "97 four injectors stuck open".