00gtr1

Do you hear any vacuum leaks? high mileage 5.4 pcv hoses like to deteriorate and cause a vacuum leak at the pcv valve or at the back of the intake. Does your scan tool show what your fuel trims are doing at idle? do you have a gauge to check fuel pressure? should be 30-35 psi. see what it does under a load. but after looking at your concern again I'd say you have some type of vacuum leak.