How does a long inlet affect a jet engine's performance?
Long, winding intake ducts can increase the drag on the airflow moving through them, reducing the amount of air which the engine can ingest as opposed to a traditional diffuser design on a nacelle.  Aircraft like the Harrier as well as the F-22, F-35 and F-117 have solved this problem with the use of large, suck in doors along the length of the intake duct in order to provide additional air mass flow during low speed or ground operations, where ram pressure cannot provide the additional airflow through the fan or engine core.