Car sputters at idle but dies when revving?

currently trying to get a 1990 ford thunderbird sc up and running. we just changed the oil, plugs and fuel filter. we had to go back and re gap the plugs as they were not far enough. after we did that it still spits and sputters not to mention lightly backfires under the hood. also when we rev the car it revs then dies. i don't know what else to do so im open to any thoughts. thanks in advance and just ask for more details if needed.