DTC p0300

I have a 2002 silverado and have recently gotten the code p0300 after my truck would not go faster than 30 miles and hour and sounded like the engine was going to explode. I have changed plugs and wire, did not work. It is the 5.3l with a coil on every cylinder. I was able to get my hands on 1 new coil and tried to move it around hoping that I could find a bad one. No luck any ideas????