95 lumina won't start after replacing plugs and fuel line

I have a 95 Chevy Lumina that won't start. While driving the RPMs would change abruptly and when took foot off gas it just died. It wouldn't start. Have replaced the plugs and fuel filter. Fuel is getting thru. the car cranks over and sounds like trying to start but will just not catch to start. Sometimes it sounds like it is backfiring.