1989 Pontiac Grand Am wont start hot

I have replaced the injectors, oil sending unit, fuel psi regulator, uel filter and the fuel psi is perfect, the car starts when it sets for a while but when its hot it wont start. the injectors are getting pulse checked with noid light, the plugs are getting fire, but when i pull the #4 injector plug it does not affect the idle, what to do next? the only code i get is knock sensor. I dont get it. the engine is a quad 4 2.3l vin D

thank you