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1995 Ford F-150 intermittent check engine light

over a year ago check engine light came on after a slight hesitation while starting engine. when engine is warming/idling up within first few minutes it stumbles a little and vibrates but then runs smooth after hitting the gas pedal a couple times. already changed out 02 and map sensors, egr and pcv valves/filter, tps sensor and fuel filter. the original cat.converter checked out o.k. why is engine light still coming on intermittantly causing idling fluctuations? and also the battery indicator gauge needle swings on low side when engine is put in reverse (happens rarely but has done it before). engine is straight 6 cylinder:)

You need to have your codes read at a parts store for free. Many will do that. Do not let them give you a diagnosis and do not buy any parts until you post the codes here in the format of P0505, P0302 etc.

An early model 95 F-150 may not be ODB-II , it may be ODB-I

Finding a parts store that can read those might be tough.