1996 Chevy Truck Engine Misfire

Everytime im driving and I reduce speed and press on the gas pedal it starts to kick like its giving to much gas. But I know its a misfire because I hear a pop noice in the exhuast.I recently did a full tune up from the cap, wires, and new plugs last year, and this year I changed the plugs but it continues to give the same flashin service engine light.