One issue at a time …
“I can pull the injector wires for cylinders 5 and 6 with no change in the idle speed”
Have you checked the injector wiring using a node light to ensure your getting a signal to trigger the injectors in question?
Next would be to check the injector flow rate by using a fuel pressure gauge attached to the fuel rail and some type of tester like this …
To see if indeed all the injectors are flowing equally and at the recommended rate.
Get through those and see what the results say.