Wont start i have a 1991 pontiac firebird formula that will spit and sputter you have to play with the gas petal to get it to stay running i have  already replaced the fuel filter and it is still doing this

Have you done a vacuum leak test?Around the injector seals is a place to start Do you have a manifold vacuum gauge and if so what is the reading that your getting?another thing to check would be the idle bypass and pcv are clear/unblocked and operating correctly.Does this happen wether engine hot or cold?or both