Low Compression / 2 cylyndrs not firing

I was driving my truck and felt a sudden surge in the decrease of power. Compression on #1&4 is about 170 but compression on # 2 and 3 is about

125. It seems to have spark but the fuel is not firing, plugs are wet and therefore only firing on only 2 cylynders. I replaced the wires but no change. What would cause this and does anyone have any ideas on the troubleshooting of the problem. Spark may be a bit weak at 2 and 3 cylynders is there a test.