2000 Dodge Durango cylinder misfire?

Very easy to test a the dealership, with the DRB we can kill the injector to cylinder 4 and monitor the engine and see how it reacts. next easyist is to move injector 4 to another cylinder and see if the misfire goes to that cylinder or stayes. confirming if it is the injector or the control circuit for cylinder 4 also the same for the spark plugs move to another cylinder and monitor. Cheaper to diagnose correctly the first time than to just replace parts hoping to fix it.