1997 Chevy Cavalier Fuel delivery

Why would raw fuel be entering only one cylinder. Other man replaced all four injecters, spark plugs and ignition wires. I replaced coil to correct random cyl misfire 0300. I guess the original problem had to do with raw fuel entering cyl #2. Spark plug does not come out soaked evry time and misfire worsens as engine warms. Cooling system holds pressure 15psi for 15 min cold and no coolant seen in cyl. Cylinder compression 125psi cold. Occasionally backfires but suspect caused by fuel in exhaust or other cylinders hunting fuel. Fuel trim is 7-14 negative and the O2 sensor is switching close to 500. Map v 5 MOT 2.75 at idle at sea level. EGR valve already ruled out and exhaust seems free flowing enough. Car occasionally runs OK but for only minutes at a time.