91 bonneville se camshaft? please help

A few months ago my engine would hesitate on acceleration and at normal driving speeds it almost felt like my tranny was slipping. I put new spark plug wires, spark plugs, changed oil, and new fuel injector. It ran a bit better but not much. Finally it just broke down and now when try to start sometimes it will start but only for no longer than a minute and that's with me giving it gas. When it dies it backfires. I am thinking it is the camshaft sensor, the interrupter-magnet, or EGR valve. Somebody help!