Chevrolet Repair: 2002 chevy silverado random misfire, crankshaft position sensor, chevy silverado

Question
I have a DTC P0300 random misfire on a 5.3 liter Vortec V8 that will not go away,I have replaced the crankshaft position sensor so far that didn't help also replaced plugs and wires still throws a P0300. I hooked up my PC based diagnostic scanner and so far the O2 sensors appear to be working normally and I also checked the MAP sensor readings and that appears normal also. Is it possible that the MAF sensor could be causing this. I unplugged it and started it up and the engine didn't idle any different. It idles very rough and it seems to get worse the longer it runs. The engine also has a severe spark ping to it when I try to accelerate or if the engine is under load. any insight on this problem would be greatly appreciated.

Answer
Did you try the injectors?  While running unplug one injector at a time and see if it changes.  If no change on the injector that is unplugged there could be the issue.  Also if it changed on all the cylinders try unplugging the coil, or do a spark test on each cylinder by removing the plug wire and grounding it to the block to see if you have spark on that cylinder.
Jimmy